Abstract: The technology described herein efficiently determines whether a real inode is shared among views, or owned. In-memory data structures include a view snapshot generation counter that is increased as a snapshot that generates a view is created, and an inode total weight. An in-memory virtual inode cache dataset for a filesystem object associated with the view is instantiated with the value of snapshot generation counter, sharing-related data based on the inode mapping file entry for the object, and an inode access weight. To determine whether the inode is shared (and needs to be split), such as on a write to the object, the in-memory data is evaluated. The real inode is shared if the generation counters are unequal, if the sharing-related data indicates sharing at an intermediate indirect block level, or indicates sharing at the inode level and the inode access weight is less than the inode total weight.

Abstract: Techniques are provided for reporting space savings due to pattern matching in storage systems. For example, in one embodiment, an exemplary method comprises, when a given allocation unit in a storage system matches one or more predefined patterns, (i) setting a corresponding pattern flag for the given allocation unit, and (ii) incrementing at least one pattern counter; generating at least one snapshot of at least a portion of a file comprising the given allocation unit; and determining a range of data reduction attributed to pattern matching based on said at least one pattern counter, wherein one extreme of said range of data reduction attributed to pattern matching excludes said one or more predefined patterns in said at least one snapshot.

Abstract: Technology described herein can perform deletion of a snapshot or portion thereof. In an embodiment, a system can comprise a processor and a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations. The operations can comprise, to delete a snapshot, or a portion of a snapshot, of a real filesystem, reading an inode mapping file (IMF) of the snapshot that indexes a virtual inode number (VIN) corresponding to a real inode. The operations further can comprise identifying the real inode of the snapshot referenced by the VIN, identifying a file object corresponding to the real inode, and deleting the file object from the snapshot.

Abstract: Technology described herein can globally perform management of virtual inode numbers (VINs) of all snapshots of a real filesystem. In an embodiment, a system can comprise a processor and a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations. The operations can comprise, in response to a request to generate a primary snapshot of a real filesystem, allocating a primary instance of an individual VIN for a virtual inode corresponding to the primary snapshot, resulting in an allocated VIN having associated therewith a weight expressed as a value. The operations further can comprise storing the weight for the allocated VIN at a corresponding VIN metadata object exclusive to the VIN.

Abstract: Optimizing file system resource reservation is presented herein. The method comprises dividing a virtual file system address space into subspaces, initializing the subspaces with volume slices of a group of volume slices comprising a first volume slice, a second volume slice, and a collection of reserved volume slices allocated based on an allocation pattern that allocates volume slices as a function of a quantitative relationship between a first value associated with a first volume slice and a second value associated with a second volume slice, determining that a data block count is insufficient to service a write operation of user data to the second volume slice; and provisioning a second subspace with a free volume slice obtained from the collection of reserved volume slices, and wherein the provisioning of the second subspace with the free volume slice is performed without invoking a memory exclusion mechanism.

Abstract: Optimizing file system resource reservation is presented herein. The method comprises dividing a virtual file system address space into subspaces, initializing the subspaces with volume slices of a group of volume slices comprising a first volume slice, a second volume slice, and a collection of reserved volume slices allocated based on an allocation pattern that allocates volume slices as a function of a quantitative relationship between a first value associated with a first volume slice and a second value associated with a second volume slice, determining that a data block count is insufficient to service a write operation of user data to the second volume slice; and provisioning a second subspace with a free volume slice obtained from the collection of reserved volume slices, and wherein the provisioning of the second subspace with the free volume slice is performed without invoking a memory exclusion mechanism.

Abstract: Technology described herein can perform deletion of a snapshot or portion thereof. In an embodiment, a system can comprise a processor and a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations. The operations can comprise, to delete a snapshot, or a portion of a snapshot, of a real filesystem, reading an inode mapping file (IMF) of the snapshot that indexes a virtual inode number (VIN) corresponding to a real inode. The operations further can comprise identifying the real inode of the snapshot referenced by the VIN, identifying a file object corresponding to the real inode, and deleting the file object from the snapshot.

Abstract: Technology described herein can globally perform management of virtual inode numbers (VINs) of all snapshots of a real filesystem. In an embodiment, a system can comprise a processor and a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations. The operations can comprise, in response to a request to generate a primary snapshot of a real filesystem, allocating a primary instance of an individual VIN for a virtual inode corresponding to the primary snapshot, resulting in an allocated VIN having associated therewith a weight expressed as a value. The operations further can comprise storing the weight for the allocated VIN at a corresponding VIN metadata object exclusive to the VIN.

Abstract: The technology described herein efficiently determines whether a real inode is shared among views, or owned. In-memory data structures include a view snapshot generation counter that is increased as a snapshot that generates a view is created, and an inode total weight. An in-memory virtual inode cache dataset for a filesystem object associated with the view is instantiated with the value of snapshot generation counter, sharing-related data based on the inode mapping file entry for the object, and an inode access weight. To determine whether the inode is shared (and needs to be split), such as on a write to the object, the in-memory data is evaluated. The real inode is shared if the generation counters are unequal, if the sharing-related data indicates sharing at an intermediate indirect block level, or indicates sharing at the inode level and the inode access weight is less than the inode total weight.

Abstract: A method for file system reorganization in the presence of inline compression includes obtaining a virtual block pointer for an original compressed segment to be reorganized, the original compressed segment comprising compressed allocation units of data stored in a storage system, wherein the virtual block pointer comprises an extent list identifying the compressed allocation units in the original compressed segment and a pointer to where the original compressed segment is stored; copying only the referenced compressed allocation units in the original compressed segment to a new compressed segment in a substantially contiguous manner; updating the extent list to identify the referenced compressed allocation units in the new compressed segment, and the pointer to where the new compressed segment is stored; and freeing the original compressed segment.

Abstract: An in-line (or foreground) approach to obtaining contiguous ranges of free space in a file system of a data storage system that can select windows having blocks suitable for relocation at a time when one or more blocks within the respective windows are freed or de-allocated. By providing the in-line or foreground approach to obtaining contiguous ranges of free space in a file system, a more efficient determination of windows having blocks suitable for relocation can be achieved, thereby conserving processing resources of the data storage system.

Abstract: Techniques for limiting storage consumed by a file system without shrinking a volume upon which the file system is deployed. The techniques are employed in a clustered environment including multiple NAS nodes, each having access to block storage including multiple storage devices. By deploying the file system on a volume of a NAS node within the clustered environment, setting the value of the FS user size to be equal to the FS volume size, and if, at a later time, it is desired to reduce the file system size, setting the value of the FS user size to a lesser value than the FS volume size, IO requests received at the NAS node can be satisfied within the logical limit of the lesser value of the FS user size without shrinking the local volume, allowing the file system size to be reduced without requiring close coordination with the block storage.

Abstract: A technique for managing storage space in a data storage system generates liability values on a per-family basis, with each family including files in the file system that are related to one another by snapping. Each family thus groups together files in the file system that generally share at least some blocks among one another based on snapshot activities. Distinct files that do not share blocks based on snapping are provided in separate families. The technique further generates worst-case storage liability of a version family by differentiating between writable data objects and read-only data objects, thus allowing administrators to provide spare storage and/or prepare for increases in storage requirements as writable data objects grow and differentiate.

Abstract: Techniques for improving storage efficiency of a data storage system are provided. The techniques include (a) performing a testing operation to evaluate whether a test condition is satisfied for a filesystem having a plurality of subspaces, each subspace being provisioned with a respective amount of storage, each subspace of the filesystem being dedicated to storing different respective types of filesystem content, wherein the test condition indicates that a first subspace has available space in excess of a threshold percentage, (b) in response to determining that the test condition is satisfied for the filesystem, performing a reduction operation on the first subspace to remove a portion of storage provisioned to that subspace while retaining the removed portion for use by the filesystem, and (c) upon a second subspace reaching a fullness threshold, provisioning the removed portion to the second subspace and storing content of the respective type of the second subspace thereon.

Abstract: A technique for managing storage space in a data storage system implements data objects in respective files. In response to an instruction to convert a set of such files from thin to thick or from thick to thin, the data storage system checks whether it has enough available storage space to accommodate the set of files if conversion were to proceed. If so, conversion is performed, and each of the set of files is converted from thin to thick or from thick to thin, in accordance with the instruction.

Abstract: Techniques for effectively measuring the amount of space saved due to deduplication and selectively turning deduplication off for a filesystem if the savings are too low are provided. The techniques include maintaining both a lower bound count and an upper bound count for block savings due exclusively to deduplication rather than due to snapshots and using an average of the lower and upper bounds to estimate the actual savings due to deduplication in order decide whether to continue operating deduplication or not.

Abstract: Techniques for limiting storage consumed by a file system without shrinking a volume upon which the file system is deployed. The techniques are employed in a clustered environment including multiple NAS nodes, each having access to block storage including multiple storage devices. By deploying the file system on a volume of a NAS node within the clustered environment, setting the value of the FS user size to be equal to the FS volume size, and if, at a later time, it is desired to reduce the file system size, setting the value of the FS user size to a lesser value than the FS volume size, IO requests received at the NAS node can be satisfied within the logical limit of the lesser value of the FS user size without shrinking the local volume, allowing the file system size to be reduced without requiring close coordination with the block storage.

Abstract: Methods and apparatus are provided for reporting space savings due to data reduction in storage systems. An exemplary method comprises establishing a leaf pointer for a plurality of allocation units of data in a storage system; for at least a first allocation unit of data matching a second allocation unit of data, replacing the leaf pointer for the first allocation unit with a deduplication pointer to the leaf pointer of the second allocation unit; determining a total number of pointers as a sum of a number of the leaf pointers and a number of the deduplication pointers; determining a difference between the total number of pointers and the number of leaf pointers; and providing a data reduction attributed to deduplication based on the difference. The allocation units of data are optionally also compressed. Data reduction attributed to the compression can optionally be determined independent of the data reduction attributed to the deduplication.

Abstract: A technique for facilitating file system operations in a data storage system provides multiple version family databases. Each version family database identifies members of a respective version family, i.e., a respective set of files in a file system that are related by file snapping. When a snap of a file is created, the file system updates a version family database for the version family that includes the file, such that the version family database identifies both the file and the snap.

Abstract: Methods and apparatus are provided for reporting space savings due to pattern matching in storage systems. An exemplary method comprises, when a given allocation unit in a storage system matches one or more predefined patterns, (i) setting a corresponding pattern flag for the given allocation unit, and (ii) incrementing at least one pattern counter; generating at least one snapshot of at least a portion of a file comprising the given allocation unit; and determining a data reduction attributed to pattern matching based on the at least one pattern counter, wherein the one or more predefined patterns in the at least one snapshot are excluded from the data reduction attributed to pattern matching.