storage device

Abstract

The present invention provides a storage device capable of reading data even when management information is damaged. The storage device (1) includes a storage device for storing data and main management information, and generates preliminary management information containing information having the same content as the main management information. At startup, one of the main management information and the preliminary management information is selected as the use management information, and the selected use management information is used to access the data stored in the storage device.

Description

Technical Field

[0001] The present invention relates to a storage device for storing data. Background Art

[0002] A disk array control device is known that controls access to a logical disk, and the logical disk is capable of distributing and storing redundant data corresponding to data on a plurality of physical disks (Patent Document 1). In the disk array control device, when a bad sector with irrecoverable data loss is detected during read access to the logical disk, a replacement sector is prepared to replace the bad sector, and missing information indicating the presence of data loss is recorded in a missing information area of ​​the replacement sector.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-293119 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] However, a storage device such as an SSD (Solid State Drive) has a problem that when management information including a conversion table for converting a logical address to a physical address is damaged, stored data cannot be accessed.

[0008] The present invention has been made in view of the above-mentioned actual situation, and one of its objects is to provide a storage device that can read data even when management information is damaged.

[0009] Solutions for solving problems

[0010] One method of the present invention for solving the problems of the above-mentioned prior art examples is a storage device, comprising: a storage unit, which includes a storage device for storing data and main management information; a preliminary generation unit, which generates preliminary management information, and the preliminary management information contains information with the same content as the main management information; and a selection unit, which, at startup, selects one of the main management information and the preliminary management information as usage management information, wherein the storage device uses the selected usage management information to access the data stored in the storage device.

[0011] According to this storage device, in addition to the main management information to be mainly used, the backup management information is generated. Therefore, even if the main management information is damaged, data can be accessed using the backup management information.

[0012] Furthermore, here, when the selection unit selects the preliminary management information as the use management information, the storage device may use the selected use management information to perform only read-only access as access to the data stored in the storage device.

[0013] In this example, since all data writing, such as data writing based on a command from the host and data rewriting in the background, is not permitted using the backup management information, rewriting of the backup management information does not occur, and damage to the backup management information can be prevented.

[0014] Furthermore, the selection unit may determine whether a predetermined circuit wiring is connected at the time of activation, and select one of the main management information and the backup management information as the use management information based on the result of the determination.

[0015] According to this example, it is possible to switch between the use of the main management information and the use of the backup management information by attaching or detaching the predetermined circuit wiring.

[0016] The storage device may further include an external interface having a plurality of wirings, and the selection unit may select one of the main management information and the backup management information as the use management information based on a connection state of the wirings of the external interface.

[0017] According to this example, it is possible to switch between the use of the main management information and the use of the backup management information according to the connection state of the wiring and the external interface.

[0018] The storage device may further include an external interface having a plurality of pins, and the selection unit may select one of the main management information and the backup management information as the use management information based on a connection state of the external interface at startup.

[0019] According to this example, it is possible to switch between the use of the main management information and the use of the backup management information according to the connection state of the external interface.

[0020] Furthermore, in other aspects of the present invention, the storage device may further include a command receiving unit for receiving a switching command, and when the command receiving unit receives the switching command, the storage device is restarted and controls the selection unit to select the preliminary management information as the usage management information.

[0021] In this example, it is possible to switch between the use of the main management information and the use of the backup management information according to the switch command.

[0022] Furthermore, in another aspect of the present invention, the storage means includes the storage device and a storage unit different from the storage device, and the preliminary management information is stored in the storage unit different from the storage device storing the main management information.

[0023] According to this example, the backup management information is stored in a storage unit different from the storage device storing the main management information, so the redundancy of the management information can be further improved.

[0024] Effects of the Invention

[0025] According to the present invention, even when the management information normally used is damaged, access to data can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a block diagram showing a configuration example of a storage device according to an embodiment of the present invention.

[0027] Figure 2 It is an explanatory diagram showing an example of management information held by a storage device according to an embodiment of the present invention.

[0028] Figure 3 This is a functional block diagram showing an example of a storage device according to an embodiment of the present invention.

[0029] Figure 4 This is a flowchart showing an example of the operation of the storage device according to the embodiment of the present invention.

[0030] Figure 5 This is another flowchart showing an example of the operation of the storage device according to the embodiment of the present invention.

[0031] Description of Reference Numerals

[0032] 1: storage device; 2: host; 11: control unit; 12: interface unit; 13: storage unit; 14: flash memory unit; 21: access processing unit; 22: preliminary generation unit; 23: selection unit. DETAILED DESCRIPTION

[0033] Embodiments of the present invention will be described with reference to the accompanying drawings. A storage device 1 according to an embodiment of the present invention is, for example, Figure 1 As shown in the example, the host computer 2 is connected to the host computer 2 and includes a control unit 11, an interface unit 12, a storage unit 13, and a flash memory unit 14. Here, the host computer 2 is a general personal computer (PC) or the like.

[0034] The control unit 11 is a program-controlled device such as a CPU, and operates according to the firmware stored in the flash memory unit 14. At the time of startup, the control unit 11 reads the firmware from the flash memory unit 14 and operates according to the read firmware.

[0035] In one example of the present embodiment, the storage device 1 is an SSD (Solid State Drive), whose storage area is divided into a plurality of blocks, and each block is further divided into pages for management. In addition, a physical block identifier is assigned to each block, and a unique physical page address is assigned to each page in each block. That is, in the present embodiment, the location where data is stored is determined based on the physical block identifier and the physical page address. That is, in the present embodiment, these physical block identifiers and physical page addresses are equivalent to physical addresses.

[0036] In addition, the host 2 specifies each storage area of ​​the storage device 1 using a logical address (LBA). The storage device 1 holds a conversion table (logical-physical table). Figure 2 As shown in the example, it is used to determine the corresponding physical address for the logical address managed by the host 2. When the storage device 1 receives an instruction to read or write data with a specified logical address from the host 2, it converts the specified logical address into a corresponding physical address. Moreover, the storage device 1 reads data from the storage area specified by the physical address obtained by the conversion, or writes data to the storage area. Such an operation of the storage device 1 is well known, so a detailed description is omitted here.

[0037] One of the features of this embodiment is that the storage device 1 holds a plurality of management information including main management information and preliminary management information as management information including a conversion table for converting the logical address to the physical address, etc. Here, the preliminary management information includes information having the same content as the main management information, and the details will be described later.

[0038] In one example of the present embodiment, at startup, the control unit 11 selects one of the main management information and the backup management information as the use management information. The control unit 11 uses the selected use management information to access the data stored in the flash memory unit 14. In addition, the control unit 11 generates the backup management information including the same information as the main management information during the period when at least the main management information is selected as the use management information and the data stored in the flash memory unit 14 is accessed. The detailed operation of the control unit 11 will be described later.

[0039] The interface unit 12 is an external interface having a plurality of signal lines (signal pins) such as a SATA (Serial AT Attachment) interface, and is connected to the host 2. The storage device 1 receives instructions for reading and writing data from the host 2 via the interface unit 12. In addition, the storage device 1 outputs the read data to the host 2 via the interface unit 12.

[0040] The storage unit 13 is one of the storage devices included in the storage device 1 of the present embodiment, and includes, for example, DRAM (Dynamic RAM). The storage unit 13 operates as a working memory of the control unit 11, and also operates as a cache memory of the flash memory unit 14. In addition, the storage unit 13 may also include SRAM (Static RAM). Furthermore, the storage unit 13 may also include, for example, NOR flash memory, serial NAND, MRAM, etc. as a non-volatile storage element or non-volatile memory device.

[0041] The flash memory unit 14 is another storage device included in the storage device 1 of this embodiment, and corresponds to the storage device of the present invention. In the example of this embodiment, the flash memory unit 14 is a NAND flash memory device. As described above, the flash memory unit 14 uses a physical address to identify a storage area that is a storage destination for data.

[0042] In addition, the flash memory unit 14 stores a program such as firmware executed by the control unit 11 at startup. Here, the program may be stored in a computer-readable and non-transitory recording medium and copied to the flash memory unit 14. The flash memory unit 14 manages the storage area by distinguishing between a main management information storage area for storing main management information and a user area for storing user data.

[0043] In addition, the firmware may also be stored in a nonvolatile storage element or nonvolatile memory device of the storage unit 13. In this case, when the storage device 1 cannot be started using the firmware stored in the flash memory unit 14 (such as when the storage area for the firmware of the flash memory unit 14 is damaged), the storage device 1 uses the firmware stored in the storage unit 13 (which may also be a ROM) to start.

[0044] Next, the operation of the control unit 11 will be described. The control unit 11 according to one example of the present embodiment implements the following operations by executing firmware: Figure 3 As illustrated, the configuration functionally includes an access processing unit 21 , a preliminary generating unit 22 , and a selecting unit 23 .

[0045] Here, the access processing unit 21 receives an instruction to read or write data from the host 2 via the interface unit 12. The access processing unit 21 accesses the flash memory unit 14 according to the received instruction. Specifically, the access processing unit 21 receives an instruction to read data from the host 2. The instruction includes a designation of a logical address indicating a location where data to be read is stored.

[0046] The access processing unit 21 acquires the physical address corresponding to the designated logical address by referring to the use management information selected by the selection unit 23. Then, the access processing unit 21 reads data from the storage destination indicated by the acquired physical address and sends the read data to the host 2.

[0047] When receiving the designation of a logical address indicating a write destination and an instruction to write data from the host 2 , the access processing unit 21 refers to the use management information selected by the selection unit 24 to acquire a physical address corresponding to the designated logical address.

[0048] Then, the access processing unit 21 investigates whether data is already stored in the block determined by the acquired physical address. If data is stored, the data in the block (hereinafter referred to as the object block) is read into the cache. In addition, the access processing unit 21 determines the physical address (referred to as the new address) of the free block that does not store data at this point in time. The access processing unit 21 overwrites the portion of the cached data determined by the acquired physical address with the indicated data, and writes at least a portion of the overwritten data to the free block. Then, the access processing unit 21 sets the data in the object block to invalid data (sets the object block to a free block). In addition, the access processing unit 21 rewrites the physical address corresponding to the logical address received from the host 2 in the usage management information to the new address. This action is well known as a read-modify-write process (RMW process), etc., so a more detailed description is omitted.

[0049] On the other hand, if the block specified by the physical address acquired by referring to the usage management information is a free block, the access processing unit 21 stores the instructed data in the free block.

[0050] When the main management information is rewritten by the RMW process, the preliminary generation unit 22 copies the rewritten main management information to generate the preliminary management information. Alternatively, the preliminary generation unit 22 may update the preliminary management information by rewriting the preliminary management information in the same manner as the rewriting performed on the main management information.

[0051] The preliminary generation unit 22 may store the generated or updated preliminary management information in the flash memory unit 14 in the same manner as the main management information. In addition, when the storage unit 13 includes a nonvolatile storage element or a nonvolatile memory device, the generated or updated preliminary management information may be stored in a nonvolatile storage element or a nonvolatile memory device of the storage unit 13 that is different from the storage device that stores the main management information.

[0052] In the present embodiment, the timing when the preliminary generating unit 22 generates or updates the preliminary management information is not limited to the timing when the main management information is updated, but may be set to each time a predetermined time has passed or each time the main management information is updated a predetermined number of times.

[0053] Furthermore, in one example of the present embodiment, when the storage device 1 rewrites the preliminary management information by performing the above-mentioned RMW process or the like when the preliminary management information is set as the use management information (when starting in a non-normal mode), the storage device 1 copies the rewritten preliminary management information to generate the main management information. Alternatively, the storage device 1 may update the main management information by rewriting the main management information in the same manner as the rewriting performed on the preliminary management information.

[0054] However, when the preliminary management information is set as the use management information (when the system is started in a non-normal mode), the access processing unit 21 may not receive the write instruction of all data (set to prohibit writing). In this case, since the preliminary management information and the main management information are not updated, the update process is not required. Here, the data write instruction includes not only the instruction based on the command from the host 2, but also the instruction formed when rewriting is performed in the background processing (processing of useless information collection, etc.) in the storage device 1. In one example of the present embodiment, during the startup in a non-normal mode, control is performed so that writing and rewriting of all data are not performed.

[0055] When the storage device 1 is started, the selection unit 23 determines whether to start in a mode (normal mode) for accessing the flash memory unit 14 using the main management information or in a mode (non-normal mode) for accessing the flash memory unit 14 using the backup management information based on a predetermined judgment criterion.

[0056] Here, the predetermined judgment criterion may be, for example, whether a predetermined circuit wiring is connected. Specifically, it may be whether a predetermined signal line (e.g., GPIO (General Purpose I / O)) of the interface unit 12 is at a high level (High) (whether the GPIO is connected to a line at a high level). As an example, when the storage device 1 is started, the selection unit 23 checks whether the GPIO of the interface unit 12 is at a high level. Then, if the GPIO of the interface unit 12 is at a high level, the selection unit 23 is set to start in a mode (normal mode) in which the flash memory unit 14 is accessed using the main management information, and the use management information is set as the main management information. In addition, in this example, when the storage device 1 is started, if the GPIO of the interface unit 12 is not at a high level, the selection unit 23 is set to start in a mode (non-normal mode) in which the flash memory unit 14 is accessed using the preliminary management information, and the use management information is set as the preliminary management information.

[0057] [action]

[0058] This embodiment has the structure of the above example and operates as follows. When the storage device 1 of this embodiment is activated, it starts to Figure 4 The illustrated processing determines whether to start up in a mode (normal mode) for accessing the flash memory unit 14 using main management information or in a mode (non-normal mode) for accessing the flash memory unit 14 using backup management information based on a predetermined judgment criterion (S11: determine mode).

[0059] Specifically, in step S11, the storage device 1 checks whether the GPIO of the interface unit 12 is at a high level (High). If it is at a high level, the storage device 1 is set to start in a mode (normal mode) for accessing the flash memory unit 14 using the main management information (S11: normal mode), and the use management information is set as the main management information (S12). In addition, in step S11, if the GPIO of the interface unit 12 is not at a high level, the storage device 1 is set to start in a mode (non-normal mode) for accessing the flash memory unit 14 using the backup management information (S11: non-normal mode), and the use management information is set as the backup management information (S13).

[0060] Next, the storage device 1 operates according to the instruction input from the host 2. When receiving a data read instruction from the host 2 via the interface unit 12 (S14), the storage device 1 refers to the use management information selected in step S12 or S13 to obtain a physical address corresponding to the logical address specified in the read instruction (S15). The storage device 1 reads data from the storage destination indicated by the obtained physical address (S16), and sends the read data to the host 2 (S17).

[0061] In addition, if Figure 5 As shown, when the storage device 1 receives the designation of the logical address indicating the write destination and the instruction to write data from the host 2 after step S12 or S13 (S21: receiving the write instruction), it determines whether the use management information is set as the main management information or the reserve management information (S22). That is, the storage device 1 only needs to check whether the mode selected in step S11 is the normal mode or the non-normal mode.

[0062] Here, when the use management information is set as the reserve management information (S22: reserve management information), the storage device 1 notifies the host 2 of an error indicating that writing is prohibited (S23), and continues the process.

[0063] In this example, the host 2 receives the notification and presents an error indicating that data writing is impossible to the user who has issued a data writing instruction.

[0064] When the use management information is set as the main management information in step S22 (S22: main management information), the storage device 1 refers to the main management information serving as the use management information to acquire the physical address corresponding to the designated logical address (S24).

[0065] The storage device 1 performs RMW processing (S25) on the data in the block (object block) determined by the acquired physical address. That is, the storage device 1 reads the data in the object block into the cache. In addition, the storage device 1 determines the physical address (new address) of the block to be the free block. Then, the storage device 1 overwrites the portion of the cached data determined by the acquired physical address with the indicated data, and writes the at least partially overwritten data (data of one block) to the block determined by the new address. In addition, the storage device 1 sets the data in the object block to invalid data to set the object block as a free block.

[0066] At this time, the storage device 1 rewrites the physical address corresponding to the logical address received from the host 2 in the main management information as the use management information, with the new address (S26: update the main management information).

[0067] Thereafter, the storage device 1 copies the main management information and stores it in the storage unit 13 as the backup management information (S27).

[0068] While the storage device 1 is operating in the normal mode, main management information updated by a process such as data writing is recorded separately as the backup management information.

[0069] When the main management information cannot be read, the user connects the GPIO of the interface unit 12 to a high level line to activate the storage device 1. The connection here may be a method of inserting a jumper or a method of connecting a circuit using a dip switch.

[0070] The storage device 1 checks whether the GPIO of the interface unit 12 is at a high level when starting up. If not, the storage device 1 starts up in a non-normal mode and operates by setting the use management information as the reserve management information.

[0071] In the example of this embodiment, data is read by referring to the separately recorded preliminary management information, so even if the main management information is damaged, data can be read. In addition, during the period when the preliminary management information is set as the use management information, writing is prohibited (set to read-only), so, for example, when a plurality of bad sectors are generated in the flash memory unit 14, the progress of further damage can be delayed, and the possibility of reading can be increased.

[0072] [Other examples of mode switching]

[0073] In the above description, the switching between the normal mode and the abnormal mode is performed according to whether the GPIO of the interface unit 12 is at a high level, but the present embodiment is not limited thereto. For example, the storage device 1 may be started in the normal mode when the GPIO of the interface unit 12 is at a low level during startup, and may be started in the abnormal mode when the GPIO is at a high level.

[0074] In addition, instead of using GPIO, it is also possible to switch between the normal mode and the abnormal mode according to whether a pair of signal lines specified by the control unit 11 is short-circuited or open-circuited. Here, the signal line can use a command output signal line that outputs a command to the peripheral circuit and a response input signal line that receives an input of a response from the peripheral circuit. In the case of this example, at startup, the control unit 11 outputs a specified command via the command output signal line to check the input from the response input signal line. Here, in the case where the outputted specified command remains input from the response input signal line as it is, the control unit 11 determines that the signal line is short-circuited and starts in the abnormal mode. In other words, the use management information is set as the preliminary management information. On the other hand, at startup, when the control unit 11 outputs a specified command via the command output signal line, if the input from the response input signal line is different from the specified command, the control unit 11 determines that the signal line is open and starts in the normal mode. In other words, the use management information is set as the main management information.

[0075] Furthermore, in an example of the present embodiment, the storage device 1 can also switch between normal mode and abnormal mode based on the connection status of the pins of the interface unit 12, which is an external interface having multiple pins, when the storage device 1 is started, and select either the main management information or the preliminary management information as the usage management information.

[0076] Specifically, the storage device 1 switches between the normal mode and the abnormal mode according to the connection state of the SATA power line or signal line as the interface part 12. As an example, it can also be set to switch between the normal mode and the abnormal mode according to whether the 12V power line (the 12V power line is generally not used in the SSD) that receives the 12V input among the SATA power lines of the storage device 1 is at the GND level or is open (NC) when the storage device 1 is started. In this example, the interface part 12 is provided with a detection circuit for detecting whether the 12V power line is at the GND level or becomes an open end. When the storage device 1 is started, the output of the detection circuit is investigated to identify whether the 12V power line is at the GND level or becomes an open end. For example, when the 12V power line is at the GND level (a jumper is connected to short the 12V power line to the GND), the storage device 1 is started in the abnormal mode and the usage management information is set to the preliminary management information.

[0077] In addition, when the storage device 1 is started, based on the output of the detection circuit, when the 12V power line is open (when a jumper is not connected to short-circuit the 12V power line and GND), when a specified voltage (including 12V) is applied to the 12V power line, etc., and when the 12V power line is not at the GND level, the storage device 1 is started in normal mode and the usage management information is set as the main management information.

[0078] In addition, since SATA provides a port for separating the connector of the power line and the connector of the signal line, the storage device 1 can also switch between normal mode and abnormal mode during startup (when the power line is connected and the power is turned on), depending on whether the connector of the signal line is connected.

[0079] In this example, a user who wants to start up in the non-normal mode turns on the power of the host 2 while unplugging the connector of the signal line in the connector of the interface unit 12, and starts up the storage device 1. When starting up, the storage device 1 detects that the signal line is not connected, starts up in the non-normal mode, and sets the usage management information to the preliminary management information.

[0080] Furthermore, when the user wants to start the storage device 1 in the normal mode, the user turns on the power of the host 2 while both the connector of the power line and the connector of the signal line of the interface unit 12 are connected to the host 2 as usual, thereby starting the storage device 1. The storage device 1 detects that the signal line is connected at the time of startup, starts in the normal mode, and sets the usage management information as the main management information.

[0081] Furthermore, the storage device 1 may set the mode at the next startup to either the normal mode or the non-normal mode in accordance with a command (mode switching command) input from the host 2 .

[0082] In this example, the storage device 1 includes a nonvolatile storage unit (register) that retains the content of the mode switching command inputted last from the host 2 even when power is not supplied.

[0083] When the storage device 1 receives the input of the mode switching command from the host 2, the content of the mode switching command is retained in the above-mentioned register. At this time, the storage device 1 may also be restarted. The storage device 1 checks the content of the register at the next startup after being restarted, and when the register is empty (no input of the mode switching command is received) or the mode switching command retained in the register indicates startup in "normal mode", the storage device 1 is started in normal mode and the usage management information is set as the main management information.

[0084] On the other hand, when the mode switching command held in the register instructs startup in the "non-normal mode" after the storage device 1 is restarted or the like, the storage device 1 is started in the non-normal mode and the use management information is set to the backup management information.

[0085] In this example, when the user wants to change the mode of the storage device 1, the storage device 1 is connected to the host 2 and the host 2 is in operation, and the host 2 outputs a mode switching command for instructing to start in a desired mode. The operation of the host 2 can be performed by driver software installed in the host 2.

[0086] In this example, when the memory device 1 holds a mode switching command in the register at startup, the memory device 1 may be started in a mode corresponding to the held mode switching command and restore the contents of the register to empty.

[0087] [Effects of Embodiment]

[0088] According to this embodiment, even if the main management information normally used is damaged, data can be accessed using the backup management information. In addition, the user can explicitly instruct which of the main management information and the backup management information to use for startup.

Claims

1. A storage device, comprising: A storage unit including a storage device for storing data and main management information; a preliminary generating unit, which generates preliminary management information, the preliminary management information including information having the same content as that of the main management information; as well as a selection unit, which, when started, selects one of the main management information and the preliminary management information as the use management information, The storage device refers to the selected usage management information to obtain a physical address corresponding to the logical address specified in the received instruction, so as to access the data in the storage device stored at the obtained physical address. The preliminary generation unit generates preliminary management information including information having the same contents as those of the main management information at least during a period in which the selection unit selects the main management information as the use management information and during a period in which data stored in the storage device is accessed.

2. The storage device according to claim 1, wherein: When the selection unit selects the preliminary management information as the use management information, the storage device uses the selected use management information to perform only read-only access as access to the data stored in the storage device.

3. The storage device according to claim 1 or 2, wherein: At the time of activation, the selection unit determines whether a predetermined circuit wiring is connected, and selects one of the main management information and the preliminary management information as the use management information based on the result of the determination.

4. The storage device according to claim 1 or 2, wherein: Also provided is an external interface having a plurality of wirings, The selection unit selects one of the main management information and the preliminary management information as the use management information based on the connection state of the wiring of the external interface.

5. The storage device according to claim 1 or 2, wherein: It also has an external interface, which has a plurality of pins. The selection unit selects one of the main management information and the preliminary management information as the use management information based on the connection state of the external interface at the time of activation.

6. The storage device according to claim 1 or 2, wherein: It also includes a command receiving unit for receiving a switching command, When the command receiving unit receives the switching command, the storage device is restarted and controls the selection unit to select the preliminary management information as the use management information.

7. The storage device according to claim 1 or 2, wherein: The storage unit includes the storage device and a storage unit different from the storage device. The preliminary management information is stored in the storage unit different from the storage device storing the main management information.

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