Abstract: A method for the reverse deletion of a plurality of snapshots in a chain of snapshots is provided. The method includes in reverse order, starting from a latest snapshot in time to an earliest snapshot in time of the plurality of snapshots: identifying at least one of a first set of one or more data blocks of a snapshot that are shared with an earlier snapshot in time in the chain of snapshots or a second set of one or more data blocks of the snapshot that are owned by the snapshot and processing the second set of one or more data blocks and skipping processing the first set of one or more data blocks, wherein processing the second set of one or more data blocks comprises performing one or more actions to maintain and/or delete data blocks of the second set of one or more data blocks.

Abstract: The present disclosure is related to methods, systems, and machine-readable media for managing extent sharing between snapshots using mapping addresses. A first mapping address can be assigned to a first extent responsive to a request to write the first extent. A second mapping address can be assigned to a second extent responsive to a request to write the second extent. A snapshot can be created. A snapshot mapping address, that is monotonically increased from the second mapping address, can be assigned to the snapshot. A third mapping address, that is monotonically increased from the second mapping address, can be assigned to a third extent of the snapshot responsive to a request to write the third extent.

Abstract: At the time of deleting a snapshot, a storage system can allocate a buffer in volatile memory, scan a plurality of logical block address (LBA)-to-virtual block address (VBA) mappings included in a first tree metadata structure of the snapshot, and, for each scanned LBA-to-VBA mapping, identify in a second tree metadata structure a VBA-to-physical block address (PBA) mapping referenced by the LBA-to-VBA mapping. If the VBA-to-PBA mapping is exclusively owned by the snapshot, the storage system can add a record to the buffer that includes the VBA specified in the VBA-to-PBA mapping. The storage system can subsequently sort the records added to the buffer in VBA order and sequentially process the sorted records to remove their corresponding VBA-to-PBA mappings from the second tree metadata structure.

Abstract: System and method for managing copy-on-write (COW) B tree structures for metadata of storage objects stored in a storage system determine, when a request to modify a target storage object stored in the storage system that requires a modification of a target leaf node in a B tree structure for metadata of the target storage object is received, whether an operation sequence number of the target leaf node is greater than a snapshot sequence number of a parent snapshot of a running point of the B tree structure. When the operation sequence number is greater than the snapshot sequence number, the target leaf mode is modified in place without copying the target leaf node. When the operation sequence number is not greater than the snapshot sequence number, the target leaf node is copied as a new leaf node for the B tree structure and the new leaf node is modified.

Abstract: The present disclosure is related to methods, systems, and machine-readable media for determining shared nodes between snapshots using probabilistic data structures. A unique identifier can be assigned to each node of a first tree data structure corresponding to a first snapshot of a virtual computing instance (VCI). A first probabilistic data structure representing the first tree data structure can be created that includes hashes of the identifiers assigned to the nodes of the first tree data structure. A unique identifier can be assigned to each node of a second tree data structure corresponding to a second snapshot of the VCI. A second probabilistic data structure representing the second tree data structure can be created that includes hashes of the identifiers assigned to the nodes of the second tree data structure.

Abstract: Techniques for efficiently managing a file clone from a filesystem which supports efficient volume snapshots are provided. In some embodiments, a system may receive an instruction to remove the file clone from the filesystem. The file clone may be a point-in-time copy of metadata of an original file. The system may further—for a file map entry in a filesystem tree associated with the file clone, the file map entry indicating a data block—decrement a reference count in a reference count entry associated with the file map entry. The reference count entry may be stored in the filesystem tree according to a key and the key may comprise an identification of the original file. The system may further reclaim the data block in a storage system when the reference count is zero.

Abstract: A method for of input/output (I/O) quiescing in a write-ahead-log (WAL)-based storage system comprising a WAL, is provided. The method generally includes receiving a request to process a control operation for the storage system, determining whether a memory buffer includes payload data for one or more write requests previously received for the storage system and added to the WAL, forcing a flush of the payload data in the memory buffer to a persistent layer of the storage system when the memory buffer includes the payload data, and processing the control operation subsequent to completing the asynchronous flush, without waiting for processing of one or more other write requests in the WAL corresponding to payload data that was not added to the memory buffer prior to receiving the request to process the control operation.

Abstract: The present disclosure is related to methods, systems, and machine-readable media for deleting snapshot pages using sequence numbers and page lookups. A monotonically-increasing sequence number (SN) can be assigned to each created page of a first snapshot of a storage volume. A first snapshot sequence number (snapSN) can be assigned to the first snapshot responsive to a creation of a second snapshot, wherein the first snapSN is equal to a largest SN of the first snapshot. An SN can be assigned to each created page of the second snapshot, wherein a first page of the second snapshot is assigned an SN monotonically increased from the first snapSN. A second snapSN can be assigned to the second snapshot responsive to a creation of a third snapshot, wherein the second snapSN is equal to a largest SN of the second snapshot. An SN can be assigned to each created page of the third snapshot, wherein a first page of the third snapshot is assigned an SN monotonically increased from the second snapSN.

Abstract: System and method for managing copy-on-write (COW) B tree structures for metadata of storage objects stored in a storage system determine, when a request to modify a target storage object stored in the storage system that requires a modification of a target leaf node in a B tree structure for metadata of the target storage object is received, whether an operation sequence number of the target leaf node is greater than a snapshot sequence number of a parent snapshot of a running point of the B tree structure. When the operation sequence number is greater than the snapshot sequence number, the target leaf mode is modified in place without copying the target leaf node. When the operation sequence number is not greater than the snapshot sequence number, the target leaf node is copied as a new leaf node for the B tree structure and the new leaf node is modified.

Abstract: Techniques for efficiently managing a file clone from a filesystem which supports efficient volume snapshots are provided. In some embodiments, a system may receive an instruction to remove the file clone from the filesystem. The file clone may be a point-in-time copy of metadata of an original file. The system may further—for a file map entry in a filesystem tree associated with the file clone, the file map entry indicating a data block—decrement a reference count in a reference count entry associated with the file map entry. The reference count entry may be stored in the filesystem tree according to a key and the key may comprise an identification of the original file. The system may further reclaim the data block in a storage system when the reference count is zero.

Abstract: The present disclosure is related to methods, systems, and machine-readable media for file system event monitoring using metadata snapshots. A traditional snapshot of a virtual computing instance (VCI) can be created in a file system. The snapshot can correspond to an extent. An indication can be made that the extent is owned by a single snapshot. A metadata snapshot, corresponding to the extent, can be created without changing the indication that the extent is owned. The extent can be modified, wherein the indication that the extent is owned causes the extent to be modified without allocating a new extent.

Abstract: The present disclosure is related to methods, systems, and machine-readable media for deleting snapshots. A deletion process can be performed responsive to receiving a request to delete a snapshot of a virtual computing instance (VCI) in a file system. The deletion process can include performing a first file comparison between the snapshot and a previous snapshot to determine first extents exclusive to the snapshot, performing a second file comparison between the snapshot and a subsequent snapshot to determine second extents exclusive to the snapshot, performing a third file comparison between the first extents and the second extents to determine common extents, wherein the common extents are common to the first extents and the second extents, and deleting the common extents from the file system.

Abstract: The present disclosure is related to methods, systems, and machine-readable media for snapshot space reporting. A first probabilistic data structure can be created for a first snapshot of a virtual computing instance (VCI) in a file system based on a hash of physical block numbers of a plurality of blocks of the first snapshot. A second probabilistic data structure can be created for a second snapshot of the VCI based on a hash of physical block numbers of a plurality of blocks of the second snapshot. A space report can be determined for the first and second snapshots based on the first probabilistic data structure and the second probabilistic data structure, wherein the space report is indicative of the storage space occupied by the first and second snapshots. A file system function can be performed by reference to the space report.

Abstract: Techniques for efficiently managing a file clone from a filesystem which supports efficient volume snapshots are provided. In some embodiments, a system may receive an instruction to remove the file clone from the filesystem. The file clone may be a point-in-time copy of metadata of an original file. The system may further—for a file map entry in a filesystem tree associated with the file clone, the file map entry indicating a data block—decrement a reference count in a reference count entry associated with the file map entry. The reference count entry may be stored in the filesystem tree according to a key and the key may comprise an identification of the original file. The system may further reclaim the data block in a storage system when the reference count is zero.

Abstract: In one set of embodiments, a computer system can periodically run an unmap service configured to scan a subset of bitmaps maintained by a file system of the computer system. As part of scanning each bitmap in the subset, the unmap service can, for each bit in the bitmap: (1) check whether the bit indicates that a corresponding physical block address (PBA) on the storage backend is currently free; (2) upon determining that the bit indicates the PBA is currently free, identify an extent within the bitmap where the PBA resides; (3) check whether an unmap indicator associated with the extent indicates that at least one free PBA in the extent is not currently unmapped in the storage backend; and (4) upon determining that the unmap indicator indicates at least one free PBA in the extent is not currently unmapped in the storage backend, add the PBA to a list of PBAs to be unmapped.

Abstract: In one example, a method for writing data includes receiving a write request and performing a first type of logging process in connection with the write request, and creating a corresponding first logging record. Additionally, a second type of logging process is performed in connection with the write request, and a corresponding second logging record created, where the second type of logging process is different from the first type of logging process. Next, a determination is made, as between the two logging records, which of the logging records requires the least amount of non-volatile random access memory (NVRAM), and the logging record that requires the least amount of NVRAM is written to the NVRAM.

Abstract: In one example, a method for writing data includes receiving a write request and performing a first type of logging process in connection with the write request, and creating a corresponding first logging record. Additionally, a second type of logging process is performed in connection with the write request, and a corresponding second logging record created, where the second type of logging process is different from the first type of logging process. Next, a determination is made, as between the two logging records, which of the logging records requires the least amount of non-volatile random access memory (NVRAM), and the logging record that requires the least amount of NVRAM is written to the NVRAM.

Abstract: In one example, a method for writing data includes receiving a write request and performing a first type of logging process in connection with the write request, and creating a corresponding first logging record. Additionally, a second type of logging process is performed in connection with the write request, and a corresponding second logging record created, where the second type of logging process is different from the first type of logging process. Next, a determination is made, as between the two logging records, which of the logging records requires the least amount of non-volatile random access memory (NVRAM), and the logging record that requires the least amount of NVRAM is written to the NVRAM.

Abstract: In one example, a method for writing data includes receiving a write request and performing a first type of logging process in connection with the write request, and creating a corresponding first logging record. Additionally, a second type of logging process is performed in connection with the write request, and a corresponding second logging record created, where the second type of logging process is different from the first type of logging process. Next, a determination is made, as between the two logging records, which of the logging records requires the least amount of non-volatile random access memory (NVRAM), and the logging record that requires the least amount of NVRAM is written to the NVRAM.

Abstract: According to some embodiment, a storage system selects one or more directories within a file system as candidates for caching based on directory statistics associated with the directories, where each of the directories includes one or more file objects stored in the storage system. For each of the selected directories, the system determines whether the directory is to be cached based on a directory cache policy. The system caches the directory in a cache memory device in response to determining that the directory is to be cached.