202 results about "Copy-on-write" patented technology

A computer system has one or more software context that share use of a memory that is divided into units such as pages. In the preferred embodiment of the invention, the context are, or include, virtual machines running on a common hardware platform. The context, as opposed to merely the addresses or page numbers, of virtual memory pages that accessible to one or more contexts are examined. If two or more context pages are identical, then their memory mappings are changed to point to a single, shared copy of the page in the hardware memory, thereby freeing the memory space taken up by the redundant copies. The shared copy is ten preferable marked copy-on-write. Sharing is preferably dynamic, whereby the presence of redundant copies of pages is preferably determined by hashing page contents and performing full content comparisons only when two or more pages hash to the same key.

According to one embodiment, a computerized method comprises operations of instantiating a first virtual machine instance and a second virtual machine instance to run concurrently with the first virtual machine instance. The first virtual machine instance provides a first virtual operating environment while the second virtual machine instance is adapted to share the resources allocated to the first virtual machine instance. The second virtual machine instance is further adapted to allocate additional resources upon conducting a Copy-On Write operation.

Described are techniques used in connection with providing continuous data backups of primary storage. A first technique uses distributed partial journals and a copy of the primary storage. A distributed partial journal is used for each input port. The partial journals are periodically incorporated into a main journal in accordance with a time stamp for the data modification recorded in each partial journal entry. A second technique, a copy on write, uses the distributed partial journals without requiring a copy of the primary storage. For each write to an address, the current contents of the address is journaled before the address on primary storage is updated.

The disclosed technology facilitates recovery from storage-related failures by checkpointing copy-on-write operation sequences. An operation sequence incorporating such checkpoints into a copy-on-write can include the following: receive a write request that identifies payload data to be written to a first data store, read original data associated with the first data store, copy the original data to a second data store, record transactional information associated with the write request, generate a first checkpoint to confirm the successful recordation of the transactional information and the successful copying of the original data to the second data store, write the payload data to the first data store, acknowledge a successful completion of the copy-on-write operation sequence, and generate a second checkpoint that confirms the successful completion of such operation sequence. The first and second checkpoints are used to form a pre-failure representation of one or more storage units (or parts thereof). The checkpoints can be stored with other transactional information, to facilitate recovery in the event of a failure, and can be used to facilitate the use of optimizations to process I/O operations.

A copy method creates a copy-on-write relationship between specified source data and an original image cache for updates from a designated host application. This copy-on-write relationship involves, responsive to at least a first update of each item of source data, writing an original image of said updated item of data and its associated address to the original image cache. An application outboard of the designated host application is utilized to copy all source data to secondary media without regard to whether the data has been updated since creating the copy-on-write relationship. A specified amount of data is copied from the original image cache to the secondary media. The secondary media therefore contains contents of the source data as of the moment of forming the copy-on-write relationship.

Tile data for drawing and desktop buffers in a desktop compositor system is managed using “copy-on-write” semantics, in which tile data stored in a memory location is not transferred to another location until the tile data for one of the buffers is modified. For each tile in drawing buffers and desktop buffers, an association is maintained with a location in a tile memory, and the number of buffer tiles associated with each location is tracked. To copy a tile from one buffer to another, the tile association for the tile in the destination buffer is modified. New data for a tile of a buffer is written to the tile memory location associated with the buffer after ensuring that the tile memory location is not associated with any other tiles of any of the buffers. As a result, memory bandwidth can be considerably reduced.

In one embodiment, a user or client device communicates with a distributed file system comprised of one or more physical nodes. The data on each of the physical nodes store metadata about files and directories within the file system. Some of the embodiments permit a user to take a snapshot of data stored on the file system. The snapshot may include a single file, a single directory, a plurality of files within a directory, a plurality of directories, a path on the file system that includes nested files and subdirectories, or more than one path on the file system that each includes nested files and directories. In some embodiments, systems and methods intelligently choose whether to use copy-on-write or point-in-time copy when saving data in a snapshot version of a file whose current version is being overwritten. In some embodiments, systems and methods allow snapshot users to return from a snapshot directory to the immediate parent directory from which the user entered into the snapshot.

A system for asynchronous reads of old data blocks updated through a write-back cache includes a storage device, a write-back cache, a storage consumer, a storage processing node, and device management software. The device management software may be configured to store a new version of a data block in the write-back cache in response to an update request from the first storage consumer and to then send an update completion notification to the first storage consumer. Some time after the update completion notification has been sent, the device management software may be configured to send a previous version of the updated data block to the storage processing node, where it may be required to perform an operation such as a copy-on write operation or a snapshot update.

On demand image streaming (ODS), in one aspect, may perform both copy-on-write and copy-on-read to gradually bring data on remote storage server to a host's local disk. Prefetching may be performed during the time the resources are otherwise idle to bring in data from the remote storage server to the host's local disk. A new image format and the corresponding block device driver for a hypervisor or the like may be also provided. ODS' image format may include a header and a bitmap that indicates whether the data sectors are on local disk or remote storage server, and an image content, for instance, stored in raw format.

A differential snapshot is established and maintained for a set of files stored on a volume. Copy-on-write operations are avoided for logically insignificant moves of blocks, such as the block rearrangements characteristic of defragmentation utilities. A file system passes a block copy command to lower-level drivers that are to inform the snapshotter that a block move operation is not logically meaningful. When the logically insignificant move is of a block whose data forms part of the data captured in the snapshot virtual volume, and when the move is to a block location that is functioning as logical free space, the snapshotter can simply modify its block bitmap and update translation table entries without needing to perform a copy-on-write.

A method for coordinating access to a storage volume between several hosts, each of which has an associated log, may involve: one of the hosts requesting permission from a coordinator to perform a write to a region of the storage volume; the host storing write data for the write to an associated log; and the coordinator sending a response granting permission to perform the write to the host, where the response indicates whether an old version of data in the region of the storage volume should be relocated to a COW (Copy On Write) snapshot volume. The host may signal completion of the write to an application that initiated the write prior to performing the write to the region of the storage volume and subsequent to both storing the write data to the associated log and receiving the response from the coordinator.

In one embodiment, a user or client device communicates with a distributed file system comprised of one or more physical nodes. The data on each of the physical nodes store metadata about files and directories within the file system. Some of the embodiments permit a user to take a snapshot of data stored on the file system. The snapshot may include a single file, a single directory, a plurality of files within a directory, a plurality of directories, a path on the file system that includes nested files and subdirectories, or more than one path on the file system that each includes nested files and directories. In some embodiments, systems and methods intelligently choose whether to use copy-on-write or point-in-time copy when saving data in a snapshot version of a file whose current version is being overwritten. In some embodiments, systems and methods allow snapshot users to return from a snapshot directory to the immediate parent directory from which the user entered into the snapshot.

Copy-on-write snapshot processing is performed on a storage system in order to produce snapshots of one or more logical volumes in the storage system. The write I/O operations made to the storage system are observed for a certain period of time. Based on the observations an estimate of the size of the storage space required to preserve the snapshot data can be computed. The information can be used to provide sufficient storage space for the snapshot process.

A virtual tape storage system includes an original virtual tape library for storing data and includes snapshot virtual tape library (SVTL). The SVTL includes a snapshot of the data stored in the original virtual tape library. A host is operable to receive the snapshot data from the SVTL to perform a disaster recovery test of the original virtual tape library. The SVTL is generated from the original virtual tape library using a copy-on-write snapshot process. In an embodiment, the original virtual tape library stores the stored data on a number of virtual tape volumes (VTVs), and the SVTL includes a snapshot of those VTDs and VTVs which are required for a disaster recovery test of the original virtual tape library. In this case, the host uses the SVTL to perform the disaster recovery test of the original virtual tape library.

Various methods and systems for updating a copy-on-write snapshot based on a dirty region log are disclosed. For example, a method involves maintaining a dirty region log and updating a copy-on-write snapshot change tracking map, based on information in the dirty region log. In some embodiments, the copy-on-write snapshot change tracking map is updated in response to an indication of a dirty region log cleaning cycle. The dirty region log cleaning cycle is inhibited until after the copy-on-write snapshot change tracking map has been updated. The method can be used to update multiple copy-on-write snapshot change tracking maps, each of which is associated with a respective one of several copy-on-write snapshots, based on information in the dirty region log. Such a method can be performed by a virtualizing network device.

A data storage controller providing network attached storage and storage area network functionality comprising a network processor (37) and providing for volume management (preferably one or more of mirroring, RAID5, and copy on write backup), caching of data stored, protocol acceleration of low level protocols (preferably one or more of ATM, Ethernet, Fibre Channel, Infiniband, Serial SCSI, Serial ATA, and any other serializable protocol), and protocol acceleration of higher level protocols (preferably one or more of IP, ICMP, TCP, UDP, RDMA, RPC, security protocols, preferably one or both of IPSEC and SSL, SCSI, and file system services, preferably one or both of NFS and CIFS).