Data deletion method and device, storage medium and electronic device

Abstract

The present application discloses a data deletion method and device, a storage medium and an electronic device, wherein the data deletion method comprises: detecting deletion operations currently to be executed on M generations of protected data volumes; extracting adjacent protection data volumes of the target protection data volume from the M generations of protected data volumes when detecting that the target deletion operations currently to be executed on M generations of protected data volumes; screening out reference business data whose data dependencies meet the target deletion conditions from the adjacent protection data volumes based on the data dependencies between the target protection data volume and the adjacent protection data volumes in terms of business data; performing the target deletion operation on the target business data and the reference business data. The above technical solution is adopted to solve the problem of low data deletion efficiency of the protection data volumes in the related technology, thereby achieving the technical effect of improving the data deletion efficiency of the protection data volumes.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of computers, and more specifically, to a method and device for deleting data, a storage medium, and an electronic device. Background Art

[0002] In the storage software field, continuous data protection (CDP) technology is key to ensuring data security. It uses high-density snapshots to capture data changes in real time and restore historical states at will. While CDP technology plays an important role in providing data protection, its implementation in existing storage systems still faces efficiency bottlenecks. In particular, in scenarios where high-density snapshots are created, traditional CDP volume (i.e., protected data volume) deletion methods use a single volume granularity, resulting in recovery speeds that cannot keep up with data growth, leading to resource waste and performance bottlenecks.

[0003] Existing CDP volume deletion technology has limitations when handling dependent volumes. Deletion operations often rely on periodic background scans, which not only impacts storage performance but also increases the risk of data loss in the event of a system failure. Furthermore, single-volume granularity deletion fails to meet the demands of modern IT systems for rapid data recovery and efficient storage management. This leads to low data deletion efficiency for protected data volumes.

[0004] In the related art, there is no effective solution to the problem of low data deletion efficiency in protecting data volumes. Summary of the Invention

[0005] Embodiments of the present application provide a data deletion method and apparatus, a storage medium, and an electronic device to at least solve the problem of low data deletion efficiency of protected data volumes in related technologies.

[0006] According to one embodiment of the present application, a data deletion method is provided, which is applied to a storage system. The storage system is configured to store business data of a target business through a source data volume and generate M generations of protection data volumes for the source data volume. The M generations of protection data volumes are respectively configured to back up business data of the source data volume at different times, where M is an integer greater than 1. The method includes:

[0007] Detect pending deletion operations on M generations of protected data volumes;

[0008] When it is detected that a target deletion operation is currently to be performed on the protection data volumes of the M generations, adjacent protection data volumes of the target protection data volume are extracted from the protection data volumes of the M generations, wherein the target deletion operation is used to delete target business data stored in the target protection data volume among the protection data volumes of the M generations, and the adjacent protection data volumes are the protection data volumes of a generation adjacent to the target protection data volume;

[0009] Based on a data dependency relationship between the target protection data volume and the adjacent protection data volume in terms of business data, reference business data whose data dependency relationship satisfies a target deletion condition is screened from the adjacent protection data volume, wherein the data dependency relationship indicates a reference method between business data backed up by different protection data volumes, and the business data whose data dependency relationship satisfies the target deletion condition is business data that is not referenced by business data in a subsequent generation of protection data volumes;

[0010] The target deletion operation is performed on the target service data and the reference service data.

[0011] Optionally, the step of screening out, from the adjacent protection data volumes, reference business data whose data dependency satisfies a target deletion condition based on the data dependency relationship between the target protection data volume and the adjacent protection data volume in terms of business data, includes:

[0012] Query whether there is business data in the adjacent protection data volume to obtain a target query result;

[0013] The reference business data whose data dependency meets the target deletion condition is filtered out from the adjacent protection data volume according to the target query result.

[0014] Optionally, querying whether business data exists in the adjacent protection data volume to obtain a target query result includes:

[0015] When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is equal to 1, query whether a descendant protected data volume of the target protected data volume has business data;

[0016] When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is greater than 1 and less than M, query whether business data exists in the previous generation protected data volume and the descendant protected data volume of the target protected data volume;

[0017] When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is equal to M, query whether the previous generation protected data volume of the target protected data volume has business data;

[0018] Among them, the previous generation protection data volume is the protection data volume of the previous generation of the target protection data volume, the descendant protection data volume is the protection data volume of the next generation of the target protection data volume, and the adjacent protection data volume includes the previous generation protection data volume and / or the descendant protection data volume.

[0019] Optionally, screening out reference business data whose data dependency satisfies a target deletion condition from the adjacent protected data volume according to the target query result includes:

[0020] If the adjacent protected data volume includes a previous generation protected data volume, and the target query result indicates that candidate business data exists in the previous generation protected data volume, determining whether the target business data references the candidate business data; if the target business data references the candidate business data, determining the candidate business data as the reference business data;

[0021] In a case where the adjacent protection data volume includes a descendant protection data volume, and the target query result indicates that the candidate service data exists in the descendant protection data volume, determining the reference service data to be an empty set;

[0022] In a case where the adjacent protection data volume includes the previous-generation protection data volume and the next-generation protection data volume, and the target query result is used to indicate that candidate business data exists in both the previous-generation protection data volume and the next-generation protection data volume, determining whether the target business data references the candidate business data in the previous-generation protection data volume; and in a case where the target business data references the candidate business data in the previous-generation protection data volume, determining the candidate business data in the previous-generation protection data volume as the reference business data;

[0023] In a case where the adjacent protected data volumes include the predecessor protected data volume and the descendant protected data volume, and the target query result indicates that there is no business data to be deleted in either the predecessor protected data volume or the descendant protected data volume, determining the reference business data to be an empty set;

[0024] Among them, the previous generation protection data volume is the protection data volume of the previous generation of the target protection data volume, the descendant protection data volume is the protection data volume of the next generation of the target protection data volume, and the adjacent protection data volume includes the previous generation protection data volume and / or the descendant protection data volume.

[0025] Optionally, performing the target deletion operation on the target service data and the reference service data includes:

[0026] Detecting whether the target business data is used by business data in a protection data volume located after the target protection data volume in the M generations of protection data volumes;

[0027] When it is detected that candidate business data exists in the target business data and is applied by business data in a protection data volume subsequent to the target protection data volume, the target deletion operation is performed on other business data of the target business data except the candidate business data and the reference business data.

[0028] Optionally, the method further includes:

[0029] Detecting pending write operations on M generations of protected data volumes;

[0030] In a case where it is detected that a target write operation is currently to be performed on the protection data volumes of the M generations, a historical protection data volume of a reference protection data volume is extracted from the protection data volumes of the M generations, wherein the target write operation is used to write new business data into the reference protection data volume of the protection data volumes of the M generations, and the historical protection data volume is a protection data volume of the M generations that is a generation prior to the reference protection data volume;

[0031] Predicting whether the data dependency relationship of the dependent business data to be deleted in the historical protection data volume will satisfy the target deletion condition after the target write operation is performed, wherein the dependent business data is business data whose data dependency relationship currently does not satisfy the target deletion condition;

[0032] Deleting the dependent service data when it is predicted that the data dependency relationship of the dependent service data will satisfy the target deletion condition after the target write operation is performed;

[0033] The target write operation is performed.

[0034] Optionally, before extracting the historical protection data volume as a reference protection data volume from the M generations of protection data volumes, the method further includes:

[0035] Detecting whether a source data volume corresponding to the reference protection data volume has currently generated a protection data volume;

[0036] In the case where it is detected that the source data volume corresponding to the reference protection data volume has not currently generated a protection data volume, the target write operation is directly performed.

[0037] According to another embodiment of the present application, a data deletion device is provided, which is applied to a storage system. The storage system is configured to store business data of a target business through a source data volume and generate M generations of protection data volumes for the source data volume. The M generations of protection data volumes are respectively configured to back up business data of the source data volume at different times, where M is an integer greater than 1. The device includes:

[0038] A first detection module is used to detect pending deletion operations on M generations of protected data volumes;

[0039] a first extraction module configured to extract, upon detecting that a target deletion operation is currently to be performed on the M generations of protected data volumes, adjacent protection data volumes of a target protected data volume from the M generations of protected data volumes, wherein the target deletion operation is used to delete target business data stored in the target protection data volume among the M generations of protected data volumes, and the adjacent protection data volumes are protection data volumes of a generation adjacent to the target protection data volume;

[0040] a screening module configured to screen, from the adjacent protection data volumes, reference business data whose data dependency on business data between the target protection data volume and the adjacent protection data volumes satisfies a target deletion condition, wherein the data dependency indicates a reference method between business data backed up by different protection data volumes, and the business data whose data dependency satisfies the target deletion condition is business data that is not referenced by business data in subsequent generations of protection data volumes;

[0041] The first deletion module is configured to perform the target deletion operation on the target service data and the reference service data.

[0042] According to another embodiment of the present application, a computer program product is provided, including a computer program, wherein a processor executes the steps in any one of the above method embodiments.

[0043] According to another embodiment of the present application, a computer-readable storage medium is provided, in which a computer program is stored. The computer program is configured to execute the steps of any one of the above method embodiments when run.

[0044] According to another embodiment of the present application, an electronic device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0045] In an embodiment of the present application, a data deletion method is proposed, which is applied to a storage system. The storage system is used to store the business data of the target business through the source data volume, and generate M generations of protection data volumes for the source data volume. The M generations of protection data volumes are respectively used to back up the business data of the source data volume at different times. M is an integer greater than 1. First, the storage system detects the deletion operations currently to be executed on the M generations of protection data volumes; when it is detected that the target deletion operations currently to be executed on the M generations of protection data volumes, the storage system extracts the adjacent protection data volumes of the target protection data volume from the M generations of protection data volumes, wherein the target deletion operation is used to delete the M generations of protection data volumes. The target business data stored in the target protection data volume in the adjacent protection data volume is the protection data volume that is adjacent to the generation of the target protection data volume; then the storage system filters out the reference business data whose data dependency meets the target deletion condition from the adjacent protection data volume based on the data dependency relationship between the target protection data volume and the adjacent protection data volume on the business data, wherein the data dependency relationship is used to indicate the reference method between the business data backed up by different protection data volumes, and the business data whose data dependency relationship meets the target deletion condition is the business data that is not referenced by the business data in the protection data volume of the subsequent generation; then the storage system performs the target deletion operation on the target business data and the reference business data. In the above manner, the storage system can screen out potential reference business data that can be deleted based on the data dependency relationship between the target protection data volume and the adjacent protection data volume in business data, and delete it together with the target business data, thereby performing deletion operations on data in multiple protection data volumes at the same time, avoiding the problem of low data deletion efficiency caused by deletion at the granularity of a single protection data volume in related technologies, and greatly improving the data deletion efficiency of protection data volumes. Therefore, the above technical solution can solve the problem of low data deletion efficiency of protection data volumes in related technologies, and achieve the technical effect of improving the data deletion efficiency of protection data volumes. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a hardware structure block diagram of a computer device for a data deletion method according to an embodiment of the present application;

[0047] Figure 2 is a flow chart of a method for deleting data according to an embodiment of the present application;

[0048] Figure 3 This is a schematic diagram of a neighboring protection data volume according to an embodiment of the present application. Figure 1 ;

[0049] Figure 4 This is a schematic diagram of a neighboring protection data volume according to an embodiment of the present application. Figure 2 ;

[0050] Figure 5 This is a schematic diagram of a neighboring protection data volume according to an embodiment of the present application. Figure 3 ;

[0051] Figure 6 is a schematic diagram of a target service data deletion phase according to an embodiment of the present application;

[0052] Figure 7 is a schematic diagram of a target write operation according to an embodiment of the present application;

[0053] Figure 8 This is a structural block diagram of a data deletion device according to an embodiment of the present application;

[0054] Figure 9 is a schematic diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0055] The embodiments of the present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0056] It should be noted that the terms "first", "second", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0057] The method embodiments provided in the embodiments of the present application can be executed in a server device or a similar computing device. Taking running on a server device as an example, Figure 1 This is a hardware structure diagram of a computer device for a data deletion method according to an embodiment of the present application. Figure 1 As shown, the server device may include one or more ( Figure 1 Only one is shown) a processor 102 (the processor 102 may include but is not limited to a microprocessor MCU or a programmable logic device FPGA and other processing devices) and a memory 104 for storing data, wherein the above-mentioned server device may also include a transmission device 106 for communication functions and an input and output device 108. It will be understood by those skilled in the art that Figure 1 The structure shown is only for illustration and does not limit the structure of the above server device. Figure 1 More or fewer components than shown, or with Figure 1 Different configurations shown.

[0058] The memory 104 can be used to store computer programs, for example, software programs and modules of application software, such as the computer program corresponding to the method for deleting data in the embodiment of the present application. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, implementing the above method. The memory 104 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include a memory remotely located relative to the processor 102, and these remote memories may be connected to a server device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0059] The transmission device 106 is used to receive or send data via a network. A specific example of the aforementioned network may include a wireless network provided by a communication provider of the server device. In one embodiment, the transmission device 106 includes a network interface controller (NIC), which can be connected to other network devices via a base station to enable communication with the Internet. In another embodiment, the transmission device 106 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0060] The terms involved in the embodiments of this application are explained as follows:

[0061] CDP: Continuous Data Protection, also known as high-density snapshot technology. A CDP volume is a protected data volume.

[0062] This application proposes a method for deleting data. Before describing the optional embodiments of this application, in order to better understand the inventive concept of this application and the creativity of this solution, the relevant technologies are first described:

[0063] Traditional CDP volume deletion is performed at the granularity of a single protected data volume. If CDP volumes are created for source data volumes at a higher density (frequency), since there is usually an upper limit on the number of CDP volumes, after reaching the upper limit, each time a new CDP volume is created, an old CDP volume is deleted. At this time, the logical address of the old CDP volume needs to be reclaimed. However, when CDP volumes are created at a higher density, the deletion frequency is extremely high, resulting in the recovery speed not being able to keep up with the speed of volume deletion (referring to the deletion of business data in the CDP volume). The recovery of a single protected data volume will also cause a certain degree of resource waste. Moreover, the previous CDP volume deletion method has the problem of dependent volumes being unable to be deleted. Scanning and deletion are often performed as background tasks. In the event of a system failure, effective data recovery cannot be performed, resulting in a low efficiency in data deletion of protected data volumes.

[0064] In this embodiment, a method for deleting data is provided. Figure 2 is a flow chart of a method for deleting data according to an embodiment of the present application, such as Figure 2 As shown, the process is applied to a storage system, the storage system is used to store the business data of the target business through the source data volume, and generate M generations of protection data volumes for the source data volume. The M generations of protection data volumes are respectively used to back up the business data of the source data volume at different times, where M is an integer greater than 1. The process includes the following steps:

[0065] Step S12, detecting deletion operations to be executed on the protected data volumes of M generations;

[0066] Step S14: When it is detected that a target deletion operation is currently to be performed on the protection data volumes of the M generations, adjacent protection data volumes of the target protection data volume are extracted from the protection data volumes of the M generations, wherein the target deletion operation is used to delete the target business data stored in the target protection data volume among the protection data volumes of the M generations, and the adjacent protection data volumes are the protection data volumes of a generation adjacent to the target protection data volume;

[0067] Step S16: Based on the data dependency relationship between the target protection data volume and the adjacent protection data volume in terms of business data, reference business data whose data dependency relationship satisfies a target deletion condition is selected from the adjacent protection data volume, wherein the data dependency relationship indicates a reference method between business data backed up by different protection data volumes, and the business data whose data dependency relationship satisfies the target deletion condition is business data that is not referenced by business data in a subsequent generation of protection data volumes.

[0068] Step S18: performing the target deletion operation on the target service data and the reference service data.

[0069] Optionally, in this embodiment, the protected data volume may be, but is not limited to, a CDP volume, which stands for Continuous Data Protection volume. It is a data storage virtualization technology used to achieve continuous protection of stored data. The core functions of CDP volumes include: Real-time data capture: CDP volumes can monitor and capture changes in data stored on the volume in real time, regardless of whether these changes are caused by user operations or system activities. Historical data recovery: Through CDP technology, data can be restored to its state at any historical point in time. This means that even if data is accidentally deleted or damaged, it can be restored from the most recent or historical snapshot. Snapshot management: CDP volumes usually contain a series of data snapshots, which are arranged in chronological order. Users can select specific snapshots for data recovery as needed. Data consistency: CDP volumes ensure that the data in all snapshots is consistent, that is, at any given point in time, the data in the snapshot is complete and consistent. Reduce storage space usage: Some CDP systems use technologies such as Copy-On-Write (COW) or Redirect-On-Write (ROW) to reduce storage space usage when creating snapshots. Automated and policy-driven: CDP volumes can be created and managed automatically, executing data protection tasks based on pre-set policies and reducing manual intervention. CDP volumes are a crucial component of storage systems and are particularly suitable for industries with stringent requirements for data security and business continuity, such as finance, healthcare, and critical enterprise applications. With CDP volumes, organizations can improve data availability and reliability, reducing the risk of data loss and business interruption.

[0070] As an optional solution, the step of selecting reference business data from the adjacent protection data volumes based on the data dependency relationship between the target protection data volume and the adjacent protection data volumes in terms of business data, wherein the data dependency relationship satisfies the target deletion condition, includes:

[0071] S21, querying whether there is business data in the adjacent protection data volume to obtain a target query result;

[0072] S22: Filter out reference business data whose data dependency meets a target deletion condition from the adjacent protected data volume according to the target query result.

[0073] Optionally, in this embodiment, both the adjacent protection data volume and the target protection data volume are protection data volumes, namely, CDP volumes. The CDP volumes are assigned corresponding LBA (Logical Block Address) addresses, where business data is stored. Querying whether business data exists in the adjacent protection data volume is equivalent to querying whether business data exists at the LBA address corresponding to the adjacent protection data volume.

[0074] Unlike related technologies that use the granularity of individual protected data volumes for deletion, the storage system in this solution can filter out potentially deletable reference business data based on the business data dependencies between the target protected data volume and the adjacent protected data volumes, and delete the data simultaneously with the target business data, thereby simultaneously deleting data from multiple protected data volumes. This avoids the low data deletion efficiency caused by the granularity of individual protected data volumes in related technologies and significantly improves the efficiency of data deletion for protected data volumes.

[0075] As an optional solution, querying whether the adjacent protected data volume contains business data to obtain a target query result includes:

[0076] S31, when the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is equal to 1, query whether a descendant protected data volume of the target protected data volume has business data;

[0077] Optionally, in this embodiment, Figure 3 This is a schematic diagram of a neighboring protection data volume according to an embodiment of the present application. Figure 1 ,like Figure 3 As shown, taking M value 4 as an example, when the target protection data volume is the i-th generation protection data volume, and i is equal to 1, that is, the target protection data volume is the first generation protection data volume (marked with a key color), at this time, the target protection data volume does not have a previous generation protection data volume, so it is queried whether the descendant protection data volume of the target protection data volume (that is, the second generation protection data volume) has business data.

[0078] S32: When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is greater than 1 and less than M, query whether business data exists in the previous generation protected data volume and the descendant protected data volume of the target protected data volume;

[0079] Optionally, in this embodiment, Figure 4 This is a schematic diagram of a neighboring protection data volume according to an embodiment of the present application. Figure 2 ,like Figure 4As shown, taking M as an example, when the target protection data volume is the i-th generation protection data volume, and i is greater than 1 and less than M, for example, the target protection data volume is the second-generation protection data volume (marked with a key color), at this time, the target protection data volume has a previous-generation protection data volume and a next-generation protection data volume, so it is queried whether the previous-generation protection data volume (i.e., the first-generation protection data volume) and the next-generation protection data volume (i.e., the third-generation protection data volume) of the target protection data volume have business data.

[0080] S33: when the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is equal to M, query whether the previous generation protected data volume of the target protected data volume has business data;

[0081] Optionally, in this embodiment, Figure 5 This is a schematic diagram of a neighboring protection data volume according to an embodiment of the present application. Figure 3 ,like Figure 5 As shown, taking M as an example, when the target protection data volume is the i-th generation protection data volume and i is equal to M, that is, the target protection data volume is the 4th generation protection data volume, at this time, the target protection data volume does not have a descendant protection data volume, so it is queried whether the previous generation protection data volume of the target protection data volume (that is, the 3rd generation protection data volume) has business data.

[0082] Among them, the previous generation protection data volume is the protection data volume of the previous generation of the target protection data volume, the descendant protection data volume is the protection data volume of the next generation of the target protection data volume, and the adjacent protection data volume includes the previous generation protection data volume and / or the descendant protection data volume.

[0083] As an optional solution, the step of filtering out reference business data whose data dependency satisfies a target deletion condition from the adjacent protected data volume according to the target query result includes:

[0084] S41, if the adjacent protected data volume includes a previous-generation protected data volume, and the target query result indicates that candidate business data exists in the previous-generation protected data volume, determining whether the target business data references the candidate business data; if the target business data references the candidate business data, determining the candidate business data as the reference business data;

[0085] S42: if the adjacent protected data volume includes a descendant protected data volume, and the target query result indicates that the candidate service data exists in the descendant protected data volume, determining the reference service data to be an empty set;

[0086] S43, when the adjacent protection data volume includes the previous-generation protection data volume and the next-generation protection data volume, and the target query result is used to indicate that candidate business data exists in both the previous-generation protection data volume and the next-generation protection data volume, determining whether the target business data references the candidate business data in the previous-generation protection data volume; when the target business data references the candidate business data in the previous-generation protection data volume, determining the candidate business data in the previous-generation protection data volume as the reference business data;

[0087] S44: if the adjacent protected data volume includes the predecessor protected data volume and the descendant protected data volume, and the target query result indicates that neither the predecessor protected data volume nor the descendant protected data volume contains any business data to be deleted, determining the reference business data set as an empty set;

[0088] S45, wherein the previous generation protection data volume is the protection data volume of the previous generation of the target protection data volume, the descendant protection data volume is the protection data volume of the next generation of the target protection data volume, and the adjacent protection data volumes include the previous generation protection data volume and / or the descendant protection data volume.

[0089] Optionally, in this embodiment, when it is detected that the M generations of protection data volumes are currently to be subjected to the target deletion operation, all the volumes (target protection data volumes) that are linked together to be deleted are removed from the CDP linked list. The following is explained using the valid generation CDP (begin-end) as the target protection data volume as an example. This solution will take the generation CDP volume (begin-end) of this batch of volumes to be deleted and the valid generation CDP before and after it (before-begin-end-after), where CDP (before) is the previous generation protection data volume and CDP (after) is the next generation protection data volume.

[0090] The solution proposed in this application uses an active query method to query the CDP (before-begin-end-after) results. Assume there is a series of CDP volumes with generations numbered 1, 2, 3, and 4, representing before, begin, end, and after respectively. The following is the solution for cases 2.1 to 2.6 of these generations:

[0091] Case 2.1: The query result is empty. For example, when querying CDP volumes between the 1st generation (before) and the 4th generation (after), no data to be deleted is found.

[0092] Action: Since no data to be deleted is found, the deletion operation will end immediately.

[0093] Case 2.2: The delete generation begin-end query is empty, but before / after are not empty. For example, when querying data between generations 2 (begin) and 3 (end), no data to be deleted is found, but data exists in generations 1 (before) and 4 (after).

[0094] Handling method: Since there is no data to be deleted within the specified deletion range, the deletion operation is completed, but it will not affect the data of the 1st and 4th generations.

[0095] Case 2.3: The delete generation begin-end query is not empty, and before / after are not empty. For example, when querying data between generations 2 (begin) and 3 (end), data to be deleted is found, and data also exists in generations 1 (before) and 4 (after).

[0096] Solution: Further check the dependencies of the data to be deleted. Details are as follows:

[0097] Case 2.3.1: before-begin is not empty and needs to be deleted. For example, the data of the first generation (before) depends on the data of the second generation (begin) and needs to be deleted.

[0098] Processing method: If the previous generation of generation 1 has been marked for deletion, then the data from generation 1 to generation 2 will be deleted.

[0099] Case 2.3.2: If end-after is not empty, it can be deleted. For example, the data of the 3rd generation (end) is dependent on the data of the 4th generation (after) and can be deleted.

[0100] Processing method: Since there is only one generation of valid data from the 3rd to the 4th generation, the data to be deleted from the 2nd to the 3rd generation can be deleted.

[0101] Case 2.4: The begin-end query for the deleted generation is not empty, before-begin is not empty, and end-after is empty. For example, when querying data between generations 2 (begin) and 3 (end), data to be deleted is found. There is data in generation 1 (before), but there is no data between generations 3 and 4 (end-after).

[0102] Processing method: Data to be deleted from generation 2 to generation 3 can be deleted, while data from generation 1 needs to be checked for deletion. If so, it will be marked as LxD.

[0103] Case 2.5: The begin-end query for the deleted generation is not empty, before-begin is empty, and end-after is not empty. For example, when querying data between generations 2 (begin) and 3 (end), data to be deleted is found. There is no data in generation 1 (before), but there is data in generations 3 to 4 (end-after).

[0104] Processing method: Since there is no data dependency in the first generation, the data to be deleted from the second to third generations can be deleted directly.

[0105] Case 2.6: The delete generation begin-end query is not empty, and both before-begin and end-after are not empty. For example: when querying data between generations 2 (begin) and 3 (end), data to be deleted is found, and data exists in generations 1 (before) and 4 (after).

[0106] Handling method: This situation is the same as situation 2.4. The data to be deleted from generation 2 to generation 3 can be deleted. At the same time, the data of generation 1 needs to be checked for deletion. If it can be deleted, it will be marked as LxD.

[0107] Through the above method, when facing different situations, potential reference business data that can be deleted can be screened out according to the data dependency relationship between the target protection data volume and the adjacent protection data volume in business data, and deleted together with the target business data, thereby realizing the simultaneous deletion operation of data in multiple protection data volumes, avoiding the problem of low data deletion efficiency caused by deletion at the granularity of a single protection data volume in related technologies, and greatly improving the data deletion efficiency of protection data volumes.

[0108] As an optional solution, performing the target deletion operation on the target service data and the reference service data includes:

[0109] S51, detecting whether the target business data is used by business data in a protection data volume located after the target protection data volume in the M generations of protection data volumes;

[0110] S52, when it is detected that there is alternative business data in the target business data that is applied by business data in the protection data volume after the target protection data volume, perform the target deletion operation on other business data of the target business data except the alternative business data and the reference business data.

[0111] Optionally, in this embodiment, Figure 6FIG. 1 is a schematic diagram of a target service data deletion phase according to an embodiment of the present application, such as Figure 6 As shown, it is assumed that there are currently five generations of protected data volumes (Gen 1 to Gen 5), among which, in stage 1, the deletion operation is triggered for the first three generations of protected data volumes (Gen 1 to Gen 3), that is, the business data in the CDP volumes of Gen 1 to Gen 3 are the target business data. In stage 2, it can be noticed that DATE 1 in the CDP volume of the Gen 1 generation is directly deleted because it has no dependency relationship with the subsequent generations, while DATE 2 in the CDP volume of the Gen 2 generation is dependent on the CDP volume of the Gen 4 generation. Therefore, DATE 2 belongs to the alternative business data and is prohibited from being deleted. At this time, the target deletion operation can be performed on the other business data of the target business data except the alternative business data (DATE 2) and the reference business data.

[0112] As mentioned above, DATE 2 in the Gen 2 CDP volume is dependent on the Gen 4 CDP volume. It can be understood that if DATE 2 is deleted, when the Gen 4 CDP volume is rolled back, the business data of DATE 2 will be inaccessible and considered lost. Therefore, DATE 2 is dependent on the Gen 4 CDP volume.

[0113] When performing batch deletions, the above method uses the current generation as the benchmark and queries all data in the interval between the two valid generations adjacent to the current generation. While performing batch deletions, it also identifies potential data to be deleted, completing the deletion task that traditionally requires background scanning and recovery.

[0114] As an optional solution, the method further includes:

[0115] S61, detecting write operations currently pending for M generations of protected data volumes;

[0116] S62, when it is detected that a target write operation is currently to be performed on the protection data volumes of the M generations, extracting a historical protection data volume of the reference protection data volume from the protection data volumes of the M generations, wherein the target write operation is used to write new business data to the reference protection data volume of the protection data volumes of the M generations, and the historical protection data volume is a protection data volume of the M generations that is a generation before the reference protection data volume;

[0117] S63, predicting whether the data dependency relationship of the dependent business data to be deleted in the historical protection data volume will satisfy the target deletion condition after the target write operation is performed, wherein the dependent business data is business data whose data dependency relationship currently does not satisfy the target deletion condition;

[0118] S64, deleting the dependent business data when it is predicted that the data dependency relationship of the dependent business data will satisfy the target deletion condition after the target write operation is performed;

[0119] S65: Execute the target write operation.

[0120] Optionally, in this embodiment, Figure 7 is a schematic diagram of a target write operation according to an embodiment of the present application, such as Figure 7 As shown in the figure, there are currently five generations of protected data volumes (Gen 1 to Gen 5). Among them, in stage 2, the deletion operation is triggered on the protected data volumes (Gen 2 to Gen 4). That is, the business data in the CDP volumes of Gen 2 to Gen 4 is the target business data. In stage 3, Date 3 in the CDP volume of Gen 4 is dependent on the CDP volume of Gen 5. Therefore, Date 3 is classified as candidate business data and cannot be deleted. In stage 4, the target write operation is triggered for the protection data volume Gen 5. The target write operation is used to write the newly added business data DATE 4 into the protection data volume Gen 5. At this time, DATE 3 in Gen 2 (historical protection data volume) was originally prohibited from being deleted because it was dependent on the CDP volume of the Gen 5 generation. Due to the writing of the newly added business data DATE 4, it can be predicted whether the data dependency relationship of the dependent business data DATE 3 to be deleted in the historical protection data volume Gen 2 will meet the target deletion condition after executing the target write operation. That is, in stage 4, DATE 3 in the CDP volume of the Gen 4 generation is no longer dependent on the CDP volume of the Gen 5 generation. At this time, DATE 3 can be deleted first, and then the target write operation can be executed to write the newly added business data DATE 4 into the protection data volume Gen 5.

[0121] Through the above method, when new data is written to the CDP source volume, a query will be made to see whether the new generation needs to be deleted. If deletion is required, the recovery operation of the deleted data will be completed before insertion. This recovery action triggered by new data also avoids invalid background recovery tasks and reduces the waste of invalid computing resources.

[0122] As an optional solution, before extracting the historical protection data volume for reference protection data volume from the M generations of protection data volumes, the method further includes:

[0123] S71, detecting whether a source data volume corresponding to the reference protection data volume has currently generated a protection data volume;

[0124] S72: When it is detected that the source data volume corresponding to the reference protection data volume has not currently generated a protection data volume, directly execute the target write operation.

[0125] Optionally, in this embodiment, if Figure 7 As shown, because the deletion of the dependent business data DATE 3 that is in contact with the dependency relationship before executing the target write operation of the CDP source volume (hereinafter referred to as passive deletion) may cause a certain degree of performance degradation, a mark will be added before the passive deletion to determine whether the volume has been snapshotted by CDP (that is, to detect whether the source data volume corresponding to the reference protection data volume has currently generated a protection data volume). If the CDP snapshot has not been taken, the passive deletion will no longer be performed (that is, when it is detected that the source data volume corresponding to the reference protection data volume has not currently generated a protection data volume, the target write operation will be directly executed), thereby improving the IO performance of the basic volume.

[0126] The data deletion method proposed in this application changes the traditional single-volume CDP task granularity approach to a multi-volume batch deletion method, using a new batch deletion algorithm to calculate the dependencies between generations. During volume deletion, passive CDP data recovery is introduced. When querying a volume deletion, the previous and next generations are searched for pending data. If there is previously dependent pending data, it is recovered during the current CDP volume deletion.

[0127] When inserting data (target write operation), a passive CDP data recovery task (passive deletion) is also introduced. If the current new data insertion happens to remove the dependency on the previous generation of data to be deleted, then before the data is inserted, the data to be deleted is recovered through an associated deletion. In addition, because the associated deletion before insertion may itself cause performance degradation, before the associated deletion query before data insertion, it will be determined whether the current volume has a CDP snapshot. If not, the associated deletion will not be started, and the data will be inserted directly to ensure the IO performance of the basic volume. The above solution can achieve continuous data protection while ensuring the stability of the entire storage system, and improve the efficiency of CDP volume deletion.

[0128] Through the description of the above implementation methods, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus the necessary general hardware platform, and of course it can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, computer, server, or network device, etc.) to execute the methods described in each embodiment of the present application.

[0129] This embodiment also provides a data deletion device for implementing the above-mentioned embodiments and preferred embodiments. Details already described will not be repeated. As used below, the term "module" may refer to a combination of software and / or hardware that implements a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation using hardware, or a combination of software and hardware, is also possible and contemplated.

[0130] Figure 8 is a structural block diagram of a data deletion device according to an embodiment of the present application; Figure 8 As shown, a data deletion device is applied to a storage system, the storage system is used to store business data of a target business through a source data volume, and generate M generations of protection data volumes for the source data volume, the M generations of protection data volumes are respectively used to back up the business data of the source data volume at different times, M is an integer greater than 1, and the device includes:

[0131] A first detection module 1002 is configured to detect pending deletion operations on M generations of protected data volumes;

[0132] A first extraction module 1004 is configured to extract, when detecting that a target deletion operation is currently to be performed on the M generations of protected data volumes, adjacent protection data volumes of the target protection data volume from the M generations of protected data volumes, wherein the target deletion operation is used to delete target business data stored in the target protection data volume among the M generations of protected data volumes, and the adjacent protection data volumes are protection data volumes of a generation adjacent to the target protection data volume;

[0133] A screening module 1006 is configured to screen, from the adjacent protection data volumes, reference business data whose data dependency relationship satisfies a target deletion condition based on a data dependency relationship between the target protection data volume and the adjacent protection data volumes, wherein the data dependency relationship indicates a reference method between business data backed up by different protection data volumes, and business data whose data dependency relationship satisfies the target deletion condition is business data that is not referenced by business data in subsequent generations of protection data volumes;

[0134] The first deletion module 1008 is configured to perform the target deletion operation on the target business data and the reference business data.

[0135] In an exemplary embodiment, the screening module includes:

[0136] A query unit, configured to query whether business data exists in the adjacent protected data volume and obtain a target query result;

[0137] A screening unit is configured to screen out reference business data whose data dependency satisfies a target deletion condition from the adjacent protected data volume according to the target query result.

[0138] In an exemplary embodiment, the query unit includes:

[0139] When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is equal to 1, query whether a descendant protected data volume of the target protected data volume has business data;

[0140] When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is greater than 1 and less than M, query whether business data exists in the previous generation protected data volume and the descendant protected data volume of the target protected data volume;

[0141] When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is equal to M, query whether the previous generation protected data volume of the target protected data volume has business data;

[0142] Among them, the previous generation protection data volume is the protection data volume of the previous generation of the target protection data volume, the descendant protection data volume is the protection data volume of the next generation of the target protection data volume, and the adjacent protection data volume includes the previous generation protection data volume and / or the descendant protection data volume.

[0143] In an exemplary embodiment, the screening unit comprises:

[0144] If the adjacent protected data volume includes a previous generation protected data volume, and the target query result indicates that candidate business data exists in the previous generation protected data volume, determining whether the target business data references the candidate business data; if the target business data references the candidate business data, determining the candidate business data as the reference business data;

[0145] In a case where the adjacent protection data volume includes a descendant protection data volume, and the target query result indicates that the candidate service data exists in the descendant protection data volume, determining the reference service data to be an empty set;

[0146] In a case where the adjacent protection data volume includes the previous-generation protection data volume and the next-generation protection data volume, and the target query result is used to indicate that candidate business data exists in both the previous-generation protection data volume and the next-generation protection data volume, determining whether the target business data references the candidate business data in the previous-generation protection data volume; and in a case where the target business data references the candidate business data in the previous-generation protection data volume, determining the candidate business data in the previous-generation protection data volume as the reference business data;

[0147] In a case where the adjacent protected data volumes include the predecessor protected data volume and the descendant protected data volume, and the target query result indicates that there is no business data to be deleted in either the predecessor protected data volume or the descendant protected data volume, determining the reference business data to be an empty set;

[0148] Among them, the previous generation protection data volume is the protection data volume of the previous generation of the target protection data volume, the descendant protection data volume is the protection data volume of the next generation of the target protection data volume, and the adjacent protection data volume includes the previous generation protection data volume and / or the descendant protection data volume.

[0149] In an exemplary embodiment, the first deletion module includes:

[0150] a detection unit, configured to detect whether the target business data is used by business data in a protection data volume located after the target protection data volume in the protection data volumes of the M generations;

[0151] The deletion unit is used to perform the target deletion operation on other business data of the target business data except the alternative business data and the reference business data when it is detected that the alternative business data in the target business data is applied by the business data in the protection data volume after the target protection data volume.

[0152] In an exemplary embodiment, the apparatus further comprises:

[0153] A second detection module is used to detect the write operations currently to be executed on the protected data volumes of M generations;

[0154] a second extraction module configured to extract, when detecting that a target write operation is currently to be performed on the M generations of protected data volumes, a historical protection data volume of a reference protection data volume from the M generations of protected data volumes, wherein the target write operation is used to write new business data into the reference protection data volume of the M generations of protected data volumes, and the historical protection data volume is a protection data volume of the M generations of protected data volumes that is a generation prior to the reference protection data volume;

[0155] a prediction module, configured to predict whether the data dependency relationship of the dependent business data to be deleted in the historical protection data volume will satisfy the target deletion condition after the target write operation is performed, wherein the dependent business data is business data whose data dependency relationship currently does not satisfy the target deletion condition;

[0156] a second deleting module, configured to delete the dependent business data if it is predicted that the data dependency relationship of the dependent business data will satisfy the target deletion condition after the target write operation is performed;

[0157] The first writing module is used to execute the target writing operation.

[0158] In an exemplary embodiment, the apparatus further comprises:

[0159] a third detection module, configured to detect whether a source data volume corresponding to the reference protection data volume has currently generated a protection data volume before extracting the historical protection data volume of the reference protection data volume from the protection data volumes of the M generations;

[0160] The second writing module is configured to directly execute the target writing operation when it is detected that the source data volume corresponding to the reference protection data volume has not currently generated a protection data volume.

[0161] It should be noted that the above modules can be implemented through software or hardware. For the latter, it can be implemented in the following ways, but not limited to: the above modules are all located in the same processor; or the above modules are located in different processors in any combination.

[0162] An embodiment of the present application further provides a computer program product, comprising a computer program, which, when executed by a processor, implements the steps of the method described in each embodiment of the present application; the computer program product further comprises a non-volatile computer-readable storage medium, which stores the computer program, which, when executed by a processor, implements the steps of the method described in each embodiment of the present application.

[0163] An embodiment of the present application further provides a computer-readable storage medium, in which a computer program is stored. The computer program is configured to execute the steps of any of the above method embodiments when run.

[0164] In an exemplary embodiment, the computer-readable storage medium may include, but is not limited to, various media that can store computer programs, such as a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk, or an optical disk.

[0165] An embodiment of the present application further provides an electronic device, Figure 9 is a schematic diagram of an electronic device according to an embodiment of the present application, such as Figure 9 As shown, the electronic device includes a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the steps in any one of the above method embodiments.

[0166] In an exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor, and the input / output device is connected to the processor.

[0167] For specific examples in this embodiment, reference may be made to the examples described in the above embodiments and exemplary implementation modes, and this embodiment will not be described in detail here.

[0168] Obviously, those skilled in the art should understand that the modules or steps of the present application described above can be implemented using a general-purpose computing device, they can be concentrated on a single computing device, or distributed across a network composed of multiple computing devices, they can be implemented using program code executable by the computing device, and thus, they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be performed in a different order than herein, or they can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module for implementation. Thus, the present application is not limited to any specific combination of hardware and software.

[0169] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for deleting data, characterized in that: Applied to a storage system, the storage system is used to store business data of a target business through a source data volume, and generate M generations of protection data volumes for the source data volume, the M generations of protection data volumes being used to back up business data of the source data volume at different times, where M is an integer greater than 1, the method comprising: Detect pending deletion operations on M generations of protected data volumes; When it is detected that a target deletion operation is currently to be performed on the protection data volumes of the M generations, adjacent protection data volumes of the target protection data volume are extracted from the protection data volumes of the M generations, wherein the target deletion operation is used to delete target business data stored in the target protection data volume among the protection data volumes of the M generations, and the adjacent protection data volumes are the protection data volumes of a generation adjacent to the target protection data volume; Based on a data dependency relationship between the target protection data volume and the adjacent protection data volume in terms of business data, reference business data whose data dependency relationship satisfies a target deletion condition is screened from the adjacent protection data volume, wherein the data dependency relationship indicates a reference method between business data backed up by different protection data volumes, and the business data whose data dependency relationship satisfies the target deletion condition is business data that is not referenced by business data in a subsequent generation of protection data volumes; The target deletion operation is performed on the target service data and the reference service data.

2. The method according to claim 1, characterized in that The step of screening out, from the adjacent protection data volumes, reference business data whose data dependency satisfies a target deletion condition based on the data dependency relationship between the target protection data volume and the adjacent protection data volume in terms of business data, includes: Query whether there is business data in the adjacent protection data volume to obtain a target query result; The reference business data whose data dependency meets the target deletion condition is filtered out from the adjacent protection data volume according to the target query result.

3. The method according to claim 2, characterized in that The querying whether the adjacent protection data volume contains business data to obtain a target query result includes: When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is equal to 1, query whether a descendant protected data volume of the target protected data volume has business data; When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is greater than 1 and less than M, query whether business data exists in the previous generation protected data volume and the descendant protected data volume of the target protected data volume; When the target protected data volume is an i-th generation protected data volume among M generations of protected data volumes, and i is equal to M, query whether the previous generation protected data volume of the target protected data volume has business data; Among them, the previous generation protection data volume is the protection data volume of the previous generation of the target protection data volume, the descendant protection data volume is the protection data volume of the next generation of the target protection data volume, and the adjacent protection data volume includes the previous generation protection data volume and / or the descendant protection data volume.

4. The method according to claim 2, characterized in that The step of screening out reference business data whose data dependency satisfies a target deletion condition from the adjacent protected data volume according to the target query result includes: If the adjacent protected data volume includes a previous generation protected data volume, and the target query result indicates that candidate business data exists in the previous generation protected data volume, determining whether the target business data references the candidate business data; if the target business data references the candidate business data, determining the candidate business data as the reference business data; In a case where the adjacent protection data volume includes a descendant protection data volume, and the target query result indicates that the candidate service data exists in the descendant protection data volume, determining the reference service data to be an empty set; In a case where the adjacent protection data volume includes the previous-generation protection data volume and the next-generation protection data volume, and the target query result is used to indicate that candidate business data exists in both the previous-generation protection data volume and the next-generation protection data volume, determining whether the target business data references the candidate business data in the previous-generation protection data volume; and in a case where the target business data references the candidate business data in the previous-generation protection data volume, determining the candidate business data in the previous-generation protection data volume as the reference business data; In a case where the adjacent protected data volumes include the predecessor protected data volume and the descendant protected data volume, and the target query result indicates that there is no business data to be deleted in either the predecessor protected data volume or the descendant protected data volume, determining the reference business data to be an empty set; Among them, the previous generation protection data volume is the protection data volume of the previous generation of the target protection data volume, the descendant protection data volume is the protection data volume of the next generation of the target protection data volume, and the adjacent protection data volume includes the previous generation protection data volume and / or the descendant protection data volume.

5. The method according to claim 1, wherein The performing the target deletion operation on the target service data and the reference service data includes: Detecting whether the target business data is used by business data in a protection data volume located after the target protection data volume in the M generations of protection data volumes; When it is detected that candidate business data exists in the target business data and is applied by business data in a protection data volume subsequent to the target protection data volume, the target deletion operation is performed on other business data of the target business data except the candidate business data and the reference business data.

6. The method according to claim 1, characterized in that The method further comprises: Detecting pending write operations on M generations of protected data volumes; In a case where it is detected that a target write operation is currently to be performed on the protection data volumes of the M generations, a historical protection data volume of a reference protection data volume is extracted from the protection data volumes of the M generations, wherein the target write operation is used to write new business data into the reference protection data volume of the protection data volumes of the M generations, and the historical protection data volume is a protection data volume of the M generations that is a generation prior to the reference protection data volume; Predicting whether the data dependency relationship of the dependent business data to be deleted in the historical protection data volume will satisfy the target deletion condition after the target write operation is performed, wherein the dependent business data is business data whose data dependency relationship currently does not satisfy the target deletion condition; Deleting the dependent service data when it is predicted that the data dependency relationship of the dependent service data will satisfy the target deletion condition after the target write operation is performed; The target write operation is performed.

7. The method according to claim 6, characterized in that Before extracting the historical protection data volume as a reference protection data volume from the M generations of protection data volumes, the method further includes: Detecting whether a source data volume corresponding to the reference protection data volume has currently generated a protection data volume; In the case where it is detected that the source data volume corresponding to the reference protection data volume has not currently generated a protection data volume, the target write operation is directly performed.

8. A data deletion device, characterized in that: Applied to a storage system, the storage system is used to store business data of a target business through a source data volume, and generate M generations of protection data volumes for the source data volume, the M generations of protection data volumes are respectively used to back up the business data of the source data volume at different times, where M is an integer greater than 1, the device includes: A first detection module is used to detect pending deletion operations on M generations of protected data volumes; a first extraction module configured to extract, upon detecting that a target deletion operation is currently to be performed on the M generations of protected data volumes, adjacent protection data volumes of a target protected data volume from the M generations of protected data volumes, wherein the target deletion operation is used to delete target business data stored in the target protection data volume among the M generations of protected data volumes, and the adjacent protection data volumes are protection data volumes of a generation adjacent to the target protection data volume; a screening module configured to screen, from the adjacent protection data volumes, reference business data whose data dependency on business data between the target protection data volume and the adjacent protection data volumes satisfies a target deletion condition, wherein the data dependency indicates a reference method between business data backed up by different protection data volumes, and the business data whose data dependency satisfies the target deletion condition is business data that is not referenced by business data in subsequent generations of protection data volumes; The first deletion module is configured to perform the target deletion operation on the target service data and the reference service data.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, wherein the computer program implements the steps of the method according to any one of claims 1 to 7 when executed by a processor.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

Images