Abstract: A technique for accessing replicas of file systems generates a snap (point-in-time version) of a replica on a destination site and provides access to the snap for reading and/or writing while replication operations on the replica between a source site and the destination site continue to be performed. As the snap is a separate object from the replica itself, users may access the snap without affecting the replica or disturbing ongoing replication activities. Users can also mount the snap to perform destination-driven backup operations, to test disaster recovery, and/or to perform other activities.

Abstract: A method is used in managing file deletions in storage systems. A request to delete a set of replicas of a file of a file system is received. A replica of the file represents a state of the file at a particular prior point in time. A sibling indirect block associated with a portion of the file identified for deletion is identified. The sibling indirect block includes a set of file system blocks. A set of indirect blocks associated with replicas of the file is identified. The sibling indirect block and the set of indirect blocks share a subset of the set of file system blocks where the set of indirect blocks have been identified for deletion. Weight information associated with the subset of the set of file system blocks shared among the set of indirect blocks that have been pending deletion is merged. The set of indirect blocks are processed for deletion concurrently. Metadata of the sibling indirect block is updated with the merged weight information.

Abstract: A method is used in managing data inconsistencies in file systems. A data inconsistency is detected in a file system data block of a file system. The file system includes a set of file system data blocks. Information regarding the data inconsistency is provided to a client of the file system. Based on the information, the client is enabled to determine an action for recovering from the data inconsistency.

Abstract: A technique for managing snaps of data objects is disclosed. Managing snaps of a data object hosted by a source data storage system (source) involve specifying, by the source, a set of policies for snaps of the data object stored on a destination data storage system (destination). The set of policies include a remote access policy information to designate a destination snaps as remote access enabled. The policy information is transferred to the destination enabling policy implementation on destination snaps. Destination snaps designated as remote access enabled are associated with a SCSI target at the destination. A virtual volume having virtual snaps associated with corresponding remote access enabled destination snaps is created at the source. The virtual volume is configured as a SCSI initiator, and exposed to a host providing access of destination snaps at the source; the source and destination are file systems implementing checkpoint functionality.

Abstract: Techniques for providing encryption of individual data objects in a data storage system include realizing data objects in the form of container files stored in a set of file systems, and encrypting individual ones of the data objects by encrypting the container files realizing the data objects using encryption keys associated with the individual data objects. By independently encrypting the container files that realize individual data objects, the disclosed system provides per-data object encryption. Each data object may be encrypted differently, e.g. using a different encryption key, even when multiple data objects are hosted over the same storage device or over a shared set of storage devices.

Abstract: In one embodiment, a method is performed by a computing device configured to manage a filesystem stored on persistent storage. The method includes (a) receiving a command to delete a range of a file of the filesystem, (b) removing blocks of the range from being accessible to the filesystem as part of the file, (c) overwriting a block of the range using a secure erasure technique, and (d) subsequent to overwriting the block, freeing the block for re-use by the filesystem. A data storage system, apparatus, and computer program product for performing a similar method are also provided.

Abstract: A technique for performing overwrites on shared data blocks in a file system transfers reference weights of block pointers to other block pointers that share those data blocks. To overwrite a portion of a file stored in a shared data block pointed to by a first block pointer, a file system manager locates a second block pointer in the file system that points to the same data block. The first block pointer has a first reference weight, and the second block pointer has a second reference weight. The file system manager transfers the first reference weight to the second block pointer, e.g., by replacing the second reference weight with the sum of the first reference weight and the second reference weight.

Abstract: A technique for storing data in a data storage system includes receiving, from a host, a request specifying a set of data to be written to a first file system, the first file system realized as a file within a second file system. A first log entry is created for the set of data in a first data log, which logs data to be written to the first file system, and a second log entry is created for the set of data in a second data log, which logs data to be written to the second file system. The first log entry provides a reference to the second log entry. The technique further includes storing the data in the cache page and acknowledging the host.

Abstract: There is disclosed a method for managing data storage. In one embodiment, the method comprises operating a storage processor of a first data storage system at a first location. The storage processor comprising a first distributed data manager and an IO stack arranged therein such that distributed data manager can receive a LUN outputted by IO stack. The method also comprises initiating a communication between first distributed data manager and second distributed data manager associated with a second data storage system at a second location. The method further comprises migrating stored data on first data storage system to second data storage system and providing LUN information associated with stored data to second data storage system such that a LUN identify of migrated data stored on second data storage system is similar to a LUN identity of corresponding stored data on first data storage system.

Abstract: There is disclosed a method for use in managing data storage. In one embodiment, the method comprises operating storage processors of respective data storage systems at different location. The storage processors comprising a distributed data manager and an IO stack arranged within the storage processor such that the distributed data manager can receive a LUN outputted by the IO stack. The method further comprises distributed data managers receiving LUNs outputted by their corresponding IO stacks, controlling LUN output and providing LUN output that enables active-active access to the storage systems at the respective different locations.

Abstract: A method is used in managing reclaiming storage space in file systems. Characteristics of a file system and a data service executing upon the file system are evaluated. Based on the evaluation, reclamation of storage space from the file system is affected based on a set of policies.

Abstract: A technique for replicating a file from a source data storage system (source) to a destination data storage system (destination) includes receiving, by the destination from the source, (i) file data for multiple logical extents of the file and (ii) respective tiering metadata for those logical extents. The destination selects, based on the tiering metadata, one or more storage tiers available on the destination. The destination updates a local replica of the file by placing the logical extents on the selected tier or tiers.

Abstract: Techniques are described for building, managing, and enforcing nested quota trees in a filesystem of a data storage system using internal filesystem structures. Such integrated, server-based, nested quota trees avoid the management overhead, communication delays, and slowed processing of proxy-based solutions and are thus more efficient and optimal.

Abstract: A technique for performing continuous data protection and point-in-time recovery for file systems includes performing continuous replication to maintain a replica of a file system by writing changes in the file system to a journal and then writing the changes from the journal to the replica. In response to receiving a request to roll back the replica to a previous point in time, the technique accesses the journal to identify changes made to the replica since the previous point in time and performs undo operations to undo the identified changes and restore the replica to its state at the previous point in time.

Abstract: An improved technique involves providing file system shrink capability by shrinking the size of the volume file in which an upper deck file system is stored. Along these lines, a data storage system, upon receiving a request to shrink an upper deck file system, determines a new address in the upper deck file system, based on an amount the upper deck file system is to be shrunk, to which the end-of-file (EOF) pointer of the volume file will point. The new address will have a smaller distance from the address of the file pointer than the original address to which the EOF pointer points. The data storage system then identifies nonempty data blocks of the upper deck file system that have logical addresses having a larger distance from the address of the file pointer than the second logical address.

Abstract: A method of conditionally truncating a volume file in a data storage system includes identifying counts of categories of data blocks of the volume file, including (1) a first count of blocks owned by the volume file and located after the target end-of-file, (2) a second count of blocks located after the target end-of-file and requiring relocation to before the target end-of-file, and (3) a third count of blocks being free and owned by the volume file and located before the target end-of-file. An approximation of space to be freed is generated as a difference between the first count and a value expressing an excess of the second count over the third count. When the approximation is above a predetermined threshold, then the volume file is truncated to the target end-of-file, and otherwise truncating is refrained from.

Abstract: Managing a circular transaction log in a data storage system includes receiving requests specifying data to be written to a data object served by the data storage system, and adding log entries to the log containing data specified by the requests at or after a tail of the log and before a head of the log. In response to a trigger event, a size of the log is dynamically increased by inserting additional storage space into the log at or after the tail and before the head, to account for differences between the rate at which entries are added to the log and the rate at which entries are flushed from the log. The disclosed technique may further operate to find the slot position in which each log entry is stored, based on the identifier of the log entry, after inserting the additional storage space into the log.

Abstract: An improved technique for managing data storage includes relocating allocated blocks within a range of a physical address space of a file system to free the allocated blocks. The range has a length equal to a length of one or more full stripes of a RAID group that stores content of the file system. In response to receiving data to be written to the file system, the file system arranges the data in the range of contiguous blocks and performs one or more full-stripe writes to write the data to the RAID group.

Abstract: Described are methods, systems, and apparatus, including computer program products for expanding a storage pool-backed file system. A file system expansion trigger is detected. First reserved space in the storage pool is reserved. A LUN size attribute associated with a LUN underlying the file system is increased. A file system size attribute associated with the file system is increased. First data to write to the file system is received. In response to receiving the first data, an expansion result is determined, wherein the expansion result indicates whether to expand the LUN and the file system. If the expansion result indicates to expand the LUN and the file system, a first portion of the first reserved space is provisioned and formatted. The first data is written to the file system.

Abstract: Improved techniques involve a storage processor proactively scavenging provisioned free blocks in snap container files and punching holes in the scavenged provisioned free blocks. For example, the storage processor may locate provisioned free blocks by accessing container file system metadata. The storage processor may then punch holes, i.e., release ownership of the snap container file on the identified provisioned free blocks. The storage processor may also delete or otherwise invalidate pointers to those blocks in the snap container file's inode.