Abstract: A system for creating a snapshot of a subset of a database stored as a plurality of segments in an address space, where the system includes a processor configured to determine from the segments, one or more source segments of the snapshot, and allocate, using a virtual memory creation unit for the snapshot, one or more snapshot segments within the address space, where the one or more snapshot segments are mapped to same physical memory addresses as the one or more source segments, and where the one or more source segments and/or the one or more snapshot segments are set to copy-on-write.

Abstract: Provided are a computer program product, system, and method for prefetching data blocks from a primary storage to a secondary storage system while data is being synchronized between the primary storage and secondary storage. A determination is made of data blocks to prefetch from the primary storage to the secondary controller not yet synchronized from the primary storage to the secondary storage in anticipation of future access requests for the data blocks to the secondary controller while data blocks are being synchronized between the primary storage and the secondary storage over the network. A prefetch command is sent to prefetch the determined data blocks to copy from the primary storage to the secondary controller to make available to future access requests received at the secondary controller for the determined data blocks.

Abstract: A technique controls movement of a logical unit of storage (LUN) among computerized storage. The technique involves selecting, by processing circuitry, a set of target storage locations of the computerized storage. The technique further involves performing, by the processing circuitry, performance evaluation operations on each target storage location of the selected set of target storage locations. The performance evaluation operations performed on each target storage location electronically assess a performance outcome of moving a production LUN from a source storage location of the computerized storage to that target storage location. The technique further involves moving, by the processing circuitry, the production LUN from the source storage location to a particular target storage location of the selected set of target storage locations based on a set of electronic performance assessments resulting from the performance evaluation operations performed on each target storage location.

Abstract: The disclosed computer-implemented method for provisioning containers in computer clusters may include (1) identifying a request to provision a container on a host system within a cluster, (2) determining that a missing storage layer image is not locally stored at the host system and initiating a transfer of the missing storage layer image to the host system, (3) creating the container and executing an application within the container on the host system before the missing storage layer image has been transferred to the host system, (4) remotely resolving a read request by reading from an instance of the missing storage layer image that is stored at a separate host system within the cluster, and (5) resolving a subsequent read request by reading from an instance of the missing storage layer image that is locally stored at the host system. Various other methods, systems, and computer-readable media are also disclosed.

Abstract: Methods, systems, and computer program products for container storage migration are provided herein. A computer-implemented method includes provisioning a copy-on-write union filesystem on the target host with (i) one or more network filesystem-mounted directories from the source host set to read-only and (ii) at least one directory set to read-write; identifying one or more files that have been (i) updated by a given container and (ii) copied over by the copy-on-write union filesystem; removing the one or more identified files from a directory path on the target host; copying, from the source host into the directory path on the target host, each of one or more files that have not been updated by the given container; merging the copy-on-write union filesystem and the directory path on the target host; and initiating the given container on the target host based on the merging.

Abstract: A method and apparatus for retention of active data stored in memory using multiple indexing systems for data storage. An embodiment of a method for retention of active data in a storage server includes reading data into a first location of a main memory of the storage server. The data in the first location indexes data elements in a long-term data storage in a first manner. The method further provides for copying the data from the first location into a second location in the main memory of the storage server, where the data in the second location indexing the data elements in the long-term data storage in a second manner.

Abstract: Systems and methods for copy on write storage conservation are presented. In one embodiment a copy on write storage conservation method includes creating and mounting a snapshot; mounting a snapshot; monitoring interest in the snapshot; initiating a copy on write discard process before a backup or replication is complete; and deleting the snapshot when the backup or replication is complete. In one embodiment the method also includes marking a file as do not copy on write. In one embodiment, the copy on write discard process includes discarding copy on write data when a corresponding read on the file in the snapshot is successful. Initiating a copy on write discard process can be done at a variety of levels (e.g., a file level, an extent level, a block-level, etc.).

Abstract: A disaster recovery system, including a target datastore for replicating data written to source datastores, and a checkpoint engine (i) for transmitting, at multiple times, quiesce commands to a plurality of host computers, each quiesce command including a timeout period that is adjusted at each of the multiple times, (ii) for determining, at each of the multiple times, whether acknowledgements indicating that a host has successfully stopped writing enterprise data to the source datastores, have been received from each of the host computers within the timeout period, (iii) for marking, at each of the multiple times, a cross-host checkpoint in the target datastore and reducing the timeout period for the quiesce commands at the next time, if the determining is affirmative, and (iv) for increasing, at each of the multiple times, the timeout period for the quiesce commands transmitted at the next time, if the determining is not affirmative.

Abstract: A storage system is provided with a memory region, a cache memory region, and a processor. The memory region stores the time relation information that indicates a time relationship of a data element that has been stored into the cache memory region and that is to be written to the logical region and a snapshot acquisition point of time to the primary volume. The processor judges whether or not the data element that has been stored into the cache memory region is a snapshot configuration element based on the time relation information for the data element that is to be written to a logical region of a write destination that conforms to the write request that specifies the primary volume and that has been stored into the cache memory region.

Abstract: Techniques to leverage replication to provide rolling point in time backup are described. Some embodiments are directed to techniques to provide rolling point in time backup with simplified restoration through distributed transactional re-creation. In one embodiment, for example, a technique may comprise creating a plurality of availability copies of a primary set of data; designating at least one of the plurality of availability copies as a backup copy; creating a log file that indicates changes to the primary set of data; updating the plurality of availability copies from the log file in near real time, without updating the backup copy; and restoring at least one of: the primary set of data and an availability copy using the backup copy and content resubmitted from a content contributor when an error occurs in at least one of: the primary set of data and an availability copy. Other embodiments are described and claimed.

Abstract: A technique performs a write operation. The technique involves receiving, after a snapshot of a file system is taken, a write instruction to write new data to a particular portion of the file system. The technique further involves includes reading, in response to the write instruction, metadata to determine whether the new data is a first update of the particular portion since the snapshot was taken. The metadata identifies portions of the file system which have changed since the snapshot was taken. The technique further involves, when the new data is a first update of the particular portion since the snapshot was taken, copying the original data from cache memory (i.e., from the file system buffer cache) to snapshot storage (i.e., to a dedicated save area) and, after the original data is copied, updating the original data in the cache memory with the new data.

Abstract: A disaster recovery system, including a target datastore for replicating data written to source datastores, and a checkpoint engine (i) for transmitting, at multiple times, quiesce commands to a plurality of host computers, each quiesce command including a timeout period that is adjusted at each of the multiple times, (ii) for determining, at each of the multiple times, whether acknowledgements indicating that a host has successfully stopped writing enterprise data to the source datastores, have been received from each of the host computers within the timeout period, (iii) for marking, at each of the multiple times, a cross-host checkpoint in the target datastore and reducing the timeout period for the quiesce commands at the next time, if the determining is affirmative, and (iv) for increasing, at each of the multiple times, the timeout period for the quiesce commands transmitted at the next time, if the determining is not affirmative.

Abstract: A device is provided for securely transferring digital data between at least one first computer system and at least one second computer system, including a controller that connects to at least one data store, a first transfer device connected to the controller and that receives the digital data from the first computer system and sends the data to the controller, a second transfer device connected to the controller and that receives the digital data from the controller and sends the data to the second computer system, and which is managed independently from the first transfer device. A corresponding transfer method and media containing a computer program are also provided.

Abstract: A disaster recovery system, including a target datastore for replicating data written to source datastores, and a checkpoint engine (i) for transmitting, at multiple times, quiesce commands to a plurality of host computers, each quiesce command including a timeout period that is adjusted at each of the multiple times, (ii) for determining, at each of the multiple times, whether acknowledgements indicating that a host has successfully stopped writing enterprise data to the source datastores, have been received from each of the host computers within the timeout period, (iii) for marking, at each of the multiple times, a cross-host checkpoint in the target datastore and reducing the timeout period for the quiesce commands at the next time, if the determining is affirmative, and (iv) for increasing, at each of the multiple times, the timeout period for the quiesce commands transmitted at the next time, if the determining is not affirmative.

Abstract: Reclamation of storage space in presence of copy-on-write snapshot. In one embodiment, a reclamation command is generated. In response to generating the reclamation command, first data held within one storage device is copied to another storage device via a communication link. One or more first physical memory regions of the one storage device, which stores the first data, is allocated to a first region of a data volume. The other storage device is configured to store a copy-on-write snapshot of the data volume. In response to copying the first data, de-allocate the one or more first physical memory regions from the first data volume region.

Abstract: A disaster recovery system, including a target datastore for replicating data written to source datastores, and a checkpoint engine (i) for transmitting, at multiple times, quiesce commands to a plurality of host computers, each quiesce command including a timeout period that is adjusted at each of the multiple times, (ii) for determining, at each of the multiple times, whether acknowledgements indicating that a host has successfully stopped writing enterprise data to the source datastores, have been received from each of the host computers within the timeout period, (iii) for marking, at each of the multiple times, a cross-host checkpoint in the target datastore and reducing the timeout period for the quiesce commands at the next time, if the determining is affirmative, and (iv) for increasing, at each of the multiple times, the timeout period for the quiesce commands transmitted at the next time, if the determining is not affirmative.

Abstract: This disclosure relates to a method, article of manufacture, and apparatus for backing up and restoring a registry. In some embodiments, this includes detecting one or more changes to a registry by a first thread of a backup application, wherein the backup application runs a plurality of threads, wherein a buffer is associated with each thread, generating a snapshot of the changes, storing the snapshot to the buffer associated with the first thread, synchronizing the first thread and one or more other threads in the plurality of the threads, and writing the snapshot from the buffer to a file.

Abstract: A method, computer program product, and computing system for receiving, on a cache system, a plurality of data write requests, wherein each data write request identifies a data portion to be written to a data array associated with the cache system. The data portions associated with the data write requests are written to the cache system. The data portions associated with the data write requests are queued until the occurrence of a commit event. Upon the occurrence of the commit event, a consolidated write operation is performed to write the data portions associated with the data write requests to the data array.

Abstract: Various computer-implemented methods for securing data of replicated volumes are disclosed. In one example, an exemplary method for performing such a task may include: 1) identifying a set of plexes of a replicated volume, 2) identifying, within the set of plexes, at least one non-trusted plex, 3) intercepting data to be replicated to the non-trusted plex, 4) encrypting the data to be replicated to the non-trusted plex, and then 5) writing the encrypted data to the non-trusted plex. Various other methods, systems, and computer-readable media are also disclosed.

Abstract: An electronic money system includes a plurality of electronic money terminals for withdrawing a sum of money which is spent by a user from money data which has been deposited into an information card. Utilization-history data including the number of times the information card has been utilized, and accumulated in the information card is read out at the time when data relating to the spent money is also withdrawn from the information card. Utilization-history data read out from each of the electronic money terminals are gathered and coordinated, so as to coordinate and tabulate the utilization-histories of the information card which has been utilized on any of the plurality electronic money terminals.

Abstract: A flashcopy of a source storage volume to a target storage volume is initiated. The content of the source storage volume is stored on the target storage volume in a space efficient manner. The space requirement of the stored content on the target storage volume is monitored. The flashcopy is terminated when the space requirement reaches a predetermined level. The stored content on the target storage volume is copied to a backup storage medium. A new flashcopy of the source storage volume is initiated.

Abstract: A flashcopy of a source storage volume to a target storage volume is initiated. The content of the source storage volume is stored on the target storage volume in a space efficient manner. The space requirement of the stored content on the target storage volume is monitored. The flashcopy is terminated when the space requirement reaches a predetermined level. The stored content on the target storage volume is copied to a backup storage medium. A new flashcopy of the source storage volume is initiated.

Abstract: An information retrieval system having: a client adapted for accessing a plurality of file sets stored on one of a plurality of file servers; a plurality of file servers configured to operate with a federated file system namespace; and a memory for storing re-direction information accessible by the client for identifying a request issued by the client for a file set at a first location in the namespace where the file set is located at a second, different location on one of the file servers and wherein the client in examining the re-direction information in the memory, re-directs the request to the second location in accordance with the re-direction information.

Abstract: A system and method for providing a substantially constant-time copy operation for file system objects managed by a network storage server begins by generating a new file based on metadata in a source file. The system then generates a snapshot of the source file or the logical volume in which the source file resides. The system then copies each of the indirect blocks of the source file to a corresponding location in the destination file. During the copy process, a modified set of file system operations can be executed on the destination metadata container. In response to a read request directed to a target block in the destination file, the system determines if target block has been copied. If the block has not been copied, the system provides a data segment from the corresponding data block in the snapshot. Write requests are processed by generating a new data block and adding a reference to the new data block to the target location in the destination metadata container.

Abstract: A computer-readable recording medium containing a database copying program for making a copy of a database on a remote computer being connected over a network, without causing a delay in replying to an application program. A mirroring unit copies data written on a plurality of local disks onto corresponding remote disks in the same sequence as the data was written. Upon reception of a data writing request, a data writing unit stores the data in a local disk selected as a current disk. When the data stored in the current disk reaches a maximum data capacity, the current disk manager switches the current disk to another local disk. In addition, when the data stored in the current disk reaches the maximum data capacity, an operation information manager stores operation information requesting backup of the data stored in the current disk, in a local disk selected as an operation information storage disk.

Abstract: A method, computer readable medium, and a system for reconstituting a virtual snapshot of files in a file virtualization system includes forming at a file virtualization device a virtual snapshot that includes a plurality of physical snapshots associated with one or more file storage devices participating in the virtual snapshot, receiving a request for performing an operation on one or more physical snapshots in the plurality of physical snapshots, providing the one or more physical snapshots in response to the request for performing the operation when the one or more physical snapshots exists in the virtual snapshot, and reconstituting the virtual snapshot by including the one or more physical snapshots to form a reconstituted virtual snapshot in response to the request for performing the operation when the one or more physical snapshots do not exist in the virtual snapshot.

Abstract: A method for establishing and maintaining a differential snapshot of a set of files stored on a volume is disclosed. The invention achieves processing time and disk space optimizations by avoiding copy-on-write operations for logically insignificant moves of blocks, such as the block rearrangements characteristic of defragmentation utilities. A file system enhancement enabling the passing of a block copy command from the file system to lower-level drivers, is used 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.

Abstract: A setup module saves disk signatures identifying cluster disks for at least one source volume to a device distinct from the cluster disks. A copy module copies data with a volume-level restore from at least one snapshot volume to the at least one source volume, overwriting the disk signatures identifying the cluster disks so that the cluster disks cannot be accessed. A reset module rewrites the saved disk signatures to the cluster disks.

Abstract: A system and method for lun migration between data containers, such as aggregates of a storage system is provided. A new destination lun is created on a destination aggregate. A background copy process is then started that copies all data from a source lun on a source aggregate to the destination lun. The storage system continues to process client-originated data access requests directed to the source lun while the background copying continues. Once all the data of the source lun has been copied to the destination lun, processing of data access requests to the lun(s) is quiesced by the storage system. Lun maps of the storage system are then updated and processing of the client-originated data access requests is resumed with those requests now being directed to the destination lun.

Abstract: Improved backup and storage operations are disclosed for virtual computing environments using a backup proxy server to perform storage operations on one or more virtual machine disks. The proxy server can include a module that intercepts application programming interface (API) calls, for writing backup data to a first location, prior to the data arriving on the proxy disk. During the intercept process, the data can be compressed in memory pages of the proxy server and redirected to an alternative backup disk location. The proxy server can also include a differential engine that identifies changes to the virtual machine disk at the block level since the last full backup. The differential engine can advantageously leverage memory pages of the proxy server to compare differences between signatures of blocks of the last full backup with signatures of new blocks. Subsequently, only blocks with non-matching signatures are processed for backup.

Abstract: A software transactional memory system is provided that generates and stores compressed transactional locks in a portion of object headers. The software transactional memory system allocates preferred write log memory with a predefined size of memory that corresponds to a number of bits in the compressed transactional locks. The compressed transactional locks identify write log entries in corresponding write logs in the preferred write log memory. If the preferred write log memory becomes full, additional write log memory is allocated for write log entries and subsequent transactional locks are stored uncompressed in an auxiliary memory. A pointer that may be used to locate the uncompressed transactional lock is stored in the header. If an object header with a compressed transactional lock is needed for another use, the compressed transactional lock is uncompressed and stored in the auxiliary memory. A pointer that may be used to locate the uncompressed transactional lock is stored in the header.

Abstract: A method for scrubbing a storage pool is disclosed. The method includes loading a scrub queue with a number of identifiers corresponding to a number of datasets, selecting a first identifier from the scrub queue, where the first identifier corresponds to a first dataset, initiating a scrubbing of the first dataset. The method further includes, upon receiving an indication of a requirement to pause the scrubbing, pausing the scrubbing of the first dataset, creating a bookmark recording a last location within the first dataset that was scrubbed before pausing the scrubbing of the first dataset, detecting at least one change to a storage pool, and performing a modification in response to detecting the at least one change to the storage pool.

Abstract: Disclosed herein is a medium drive apparatus connected to an information processing apparatus for performing recording and reproduction on and from a recording medium in accordance with a request from the information processing apparatus, which may include an inputting and outputting section configured to record and reproduce data on and from a recording medium, and a control section configured to execute a first operation process as a reproduction only mode, a second operation process as a recording and reproduction mode, an authentication process with the information processing apparatus, and a mode changing process of changing the operation mode from the reproduction only mode to the recording and reproduction mode in response to success in the authentication by the authentication process thereby to control the recording operation and the reproduction operation of the inputting and outputting section.

Abstract: A consistent snapshot of a large main memory knowledge base is saved to persistent storage without blocking the application for the duration of serializing and writing the knowledge base. Taking the snapshot comprises bringing the knowledge base to a consistent state (in a multithreaded application), using virtual memory facilities to obtain a copy-on-write copy of the knowledge base in memory, and using a separate thread or process to serialize the copy-on-write copy to persistent storage.

Abstract: A method, computer readable medium, and a system for reconstituting a virtual snapshot of files in a file virtualization system includes forming at a file virtualization device a virtual snapshot that includes a plurality of physical snapshots associated with one or more file storage devices participating in the virtual snapshot, receiving a request for performing an operation on one or more physical snapshots in the plurality of physical snapshots, providing the one or more physical snapshots in response to the request for performing the operation when the one or more physical snapshots exists in the virtual snapshot, and reconstituting the virtual snapshot by including the one or more physical snapshots to form a reconstituted virtual snapshot in response to the request for performing the operation when the one or more physical snapshots do not exist in the virtual snapshot.

Abstract: 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.

Abstract: Provided are a method, system, and program for using a heartbeat signal to maintain data consistency for writes to source storage copied to target storage. A copy relationship associates a source storage and target storage pair, wherein writes received at the source storage are transferred to the target storage. A determination is made whether a signal has been received from a system within a receive signal interval. A freeze operation is initiated to cease receiving writes at the source storage from an application in response to determining that the signal has not been received within the receive signal interval. A thaw operation is initiated to continue receiving write operations at the source storage from applications after a lapse of a freeze timeout in response to the freeze operation, wherein after the thaw operation, received writes completed at the source storage are not transferred to the target storage.

Abstract: Servers in a network cluster can each store a copy of a data item in local cache, providing read access to these copies through read-only entity beans. The original data item in the database can be updated through a read/write entity bean one of the cluster servers. That cluster server has access to an invalidation target, which contains identification information relating to copies of the data item stored on servers in the cluster. Once the read/write bean updates the data item in the database, an invalidate request can be sent or multicast to all cluster members, or to any read-only bean or server contained in the invalidation target. Each server or read-only bean receiving the request knows to drop any copy of the data item in local cache, and can request a current copy of the data item from the database.

Abstract: Data is migrated from a first CAS (contents addressed storage) system to a second CAS system. When the migration process is started, the second CAS system retrieves a list of the objects stored on the first CAS system. The second CAS system, based on the list, retrieves each object from the first CAS system, calculates an object ID for each object, and stores each object and the calculated object ID into the storage devices in the second CAS system. Methods for reducing downtime during the migration process are also disclosed.

Abstract: A method and apparatus for providing single instance restoration of data files is provided. In one embodiment, a method for using a signature database to provide a single instance data restoration solution includes processing a restore request for a data file, wherein the data file is associated with a signature and examining a signature database using the signature to identify at least one locally available data file having at least one signature that matches the signature associated with the data file.

Abstract: Various embodiments include one or more of systems, methods, software, and data structures that allow dual access to concurrent data in a database management system including uncommitted updated data. Some embodiments include a dual snapshot of data in a multi-version concurrency control style database, but the embodiments described herein are equally applicable to virtually any other type of database and database management system.

Abstract: Techniques for continuous data protection can include creating snapshots of one or more underlying storage volumes upon specific file system events. Generating snapshots upon every file close event can protect the files in a storage system by keeping a snapshot of every version or modification of each file. Removal of redundant snapshots can mitigate the impact on storage capacity associated with creating these large numbers of volume snapshots upon each file close event. Additionally, file closure lists can be employed to allow generating snapshots only when a previously closed file is reopened. Such an approach can protect the previous version of a file prior to the opening of a new version of the file. Such an approach can also mitigate storage capacity impact without the creation of redundant snapshots.

Abstract: Establishing a plurality of storage areas includes associating each of a first plurality of storage areas of a first type that contain sections of data with corresponding ones of second plurality of storage areas of a second type having pointers to alternative sections of data storage areas of the first type, where initially none of the second plurality of storage areas is available for accessing data corresponding thereto, and, after associating all of the first and second plurality of storage areas, activating the second plurality of storage areas to make the second plurality of storage areas available for accessing data. Exclusive access may be enabled for all of the first plurality of storage areas prior to activating the second plurality of storage areas or to each storage area one at a time.

Abstract: In one embodiment, a user or client device is connected to 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. According to one embodiment, the system stores and updates metadata, including a governance list, for each of the files and directories. The governance list provides a representation of the snapshots which govern a file or directory and its descendants.

Abstract: A system includes at least a user and a file system connected to the user through a network. An estimated write size of a write operation of the user into the file system is managed as an accumulated value. The timing of judging the limit of the disk usage amount is specified from the accumulated value and a predetermined threshold value, and the limit of the disk usage amount is judged at the specified timing, so that disk usage amount by a user may be limited and managed.

Abstract: Techniques are presented for snapshotting. Blocks associated with a storage volume are frozen from volatile access upon receipt of a snapshot request. Continued volatile access to the frozen blocks is permitted by transparently mapping each frozen block to an available block within the volume that is not associated with the snapshot. Volatile access continues on the available blocks.

Abstract: A system and method of creating a snapclone for on-line point-in-time complete backup in a virtualized storage system is disclosed. In one embodiment, a method for creating a snapclone for on-line point-in-time complete backup in a virtualized storage system includes receiving a copy operation directed to one or more identified segments of an original virtual disk, in response to the copy operation, substantially sequentially copying the one or more identified segments to a snapclone virtual disk, clearing bits in an in-memory sharing bitmap associated with already copied one or more identified segments, and writing the cleared bits in the in-memory sharing bitmap to a disk resident virtual disk metadata associated with the snapclone virtual disk upon receiving a current write I/O operation while the copy operation is in progress. The received current write I/O operation is targeting data outside the LBA range of the already copied one or more identified segments.

Abstract: A consistent snapshot of a large main memory knowledge base is saved to persistent storage without blocking the application for the duration of serializing and writing the knowledge base. Taking the snapshot comprises bringing the knowledge base to a consistent state (in a multithreaded application), using virtual memory facilities to obtain a copy-on-write copy of the knowledge base in memory, and using a separate thread or process to serialize the copy-on-write copy to persistent storage.

Abstract: A device and method for connection to a host and transferring data between the host and data storage assembly. The device is preferably a storage system which initializes a logical unit (LUN) in the storage assembly. A persistent memory stores a data representation of clean areas in the LUN. The storage system receives data to be written from the host to a destination area in the LUN, and determines if the destination area in the LUN is a clean area or a dirty area as indicated in the persistent memory. The storage system effects a snapshot copy of data from the destination area in the LUN to an archive storage device of the storage assembly only if the destination area is not entirely a clean area. Bandwidth is likewise reduced in LUN copy and reconstruction operations.

Abstract: 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.