Abstract: A technique for operating a file system in a NAS (network attached storage) cluster includes discovering, by a data node running in the NAS cluster, a LUN (Logical UNit) provisioned from block storage. The data node renders the LUN as a block device and creates a local volume, built on the block device. The data node then deploys the file system on the local volume. The file system, the local volume, the block device, and the LUN all have address spaces, and the address space of each corresponds one-to-one with the address space of each of the others. Write requests directed to addresses in the file system propagate to the LUN, where they effect writes at corresponding addresses in the LUN.

Abstract: A technique for operating a file system in a NAS (network attached storage) cluster deploys a file system on a thin LUN in block storage and unilaterally provisions storage space to the file system without extending provisioning activities to the LUN. Rather, the file system proceeds as if the storage space is available from the LUN without reserving space or confirming availability.

Abstract: A technique for repairing damage to a file system stores compression headers in association with respective extents of in-line compressed data. A repair utility reads contents from the compression headers and applies the contents to repair damaged metadata structures that the file system uses to access the associated extents. In this fashion, the repair utility restores access to compressed data, which would otherwise be lost.

Abstract: A method is provided for preserving redundant copies of metadata in a data storage system employing de-duplication. The method includes (a) creating metadata describing a file of a file system stored on the data storage system, (b) buffering the metadata within a metadata buffer of system memory of the data storage system, (c) sending contents of the metadata buffer from system memory to transmission circuitry of the data storage system, (d) directing the transmission circuitry to store the contents of the metadata buffer to a first location of persistent storage of the data storage system, and (e) directing the transmission circuitry to store a modified version of the contents of the metadata buffer to a second location of persistent storage of the data storage system, the first location being different from the second location. A computerized apparatus and a computer program product are also provided for performing a similar method.

Abstract: A method, computer program product, and computing system for defining a transactional log file for a data storage system including a data array. A first plurality of IO requests for the data storage system is processed. The transactional log file is updated to include information concerning the first plurality of IO requests. An IO pointer is defined to locate a specific IO request of the first plurality of IO requests within the transactional log file. File system metadata is defined on the data array for the data storage system.

Abstract: A method, computer program product, and computing system for defining a transactional log file for a data storage system including defining a transactional log file for a data storage system including a data array. A plurality of IO requests for the data storage system are processed. The transactional log file is updated to include information concerning the plurality of IO requests, wherein the information includes an LGT indicator for each of the plurality of IO requests. The occurrence of a malfunction within the data storage system is sensed.

Abstract: A technique for managing a file system includes dividing the addressable space of a file system into multiple subspaces: a data subspace for user data; an inode subspace for inodes describing the user data; and an MDB (metadata block) subspace for indirect blocks and/or directory structures pertaining to the user data. In response to storage requests to write user files to the file system, the file system stores user data of the files in the data subspace, stores inodes pertaining to the user files in the inode subspace, and stores indirect blocks and/or directories in the MDB subspace.

Abstract: An improved technique generates formatted file system metadata in increments only when metadata for those increments are specifically requested. A location on a storage volume designated for storing file system metadata is read and tested to determine whether it stores a predetermined pattern indicating an unformatted state. If the pattern is found, metadata for the designated location are generated and returned. Otherwise, metadata are returned as initially read from the storage volume.

Abstract: An improved technique involves providing a pair of inode numbers in a directory entry for a file in a directory of a target file system. Along these lines, the target file system writes a first inode number and a second inode number to the directory entry for the file. While the client has not yet remounted its file system, that client may continue to use the file handle provided for the original file system. The data storage system continues to refer to a mapping table that cross-references initial inode numbers to target ones, at some cost in performance. Nevertheless, the client has an option to remount the file system at a time that is convenient to the client, so that the client may obtain a new handle. The client may subsequently use the new file handle to access the file.

Abstract: A dataset is recovered after a server reboot while clients access the dataset. In response to the reboot, not-yet-completed transactions in a log are parsed to create, for each of the dataset blocks modified by these active transactions, a respective block replay list of the active transactions that modify the block. Once the block replay lists have been created, clients may access specified blocks of the dataset after on-demand recovery of the specified blocks. The on-demand recovery is concurrent with a background recovery task that replays the replay lists. To accelerate log space recovery, the parsing of the log inserts each replay list into a first-in first-out queue serviced by multiple replay threads. The queue can also be used as the cache writeback queue, so that the cache index is used for lookup of the replay list and the recovery state of a given block.

Abstract: A networked data storage system includes a primary volume and a pointer-based virtual secondary volume. The secondary volume has B-tree checkpoints of the state of a primary filesystem of the primary volume. Intermediate syncpoints are declared between checkpoint checkpoints. The syncpoints are logical locations on the secondary volume where the B-tree is known to be in a consistent state. The frequency of syncpoints may be set by an administrator in units of blocks, i.e., a syncpoint to be taken every n blocks. Before performing a B-tree split, entire images of the leaves and parent node involved in the split are written to an intent log in a relatively fast transaction that may comprise a single I/O operation to contiguous memory. Movement of data between leaf nodes and changes to the parent nodes as a result of the split operation proceed asynchronously. In the event of a reboot before the split operation is complete, the intent log is used to complete the split transaction from the most recent syncpoint.

Abstract: A physical address extension feature maps multiple virtual memory spaces to an extended physical memory. A virtual space manager dynamically allocates pages of the physical memory to respective virtual spaces. The virtual space manager responds to a request from an application for allocation of a page of physical memory by returning a cookie indicating the allocated page. The virtual space manager responds to a request including the cookie by switching virtual address translation to the virtual memory space including the indicated page. The cookie is used to access a cookie cache of state information on the last page of virtual memory having been mapped into physical memory. For example, segments of the page store block map entries for snapshot copies, and the cookie cache caches the last-accessed values of the block numbers and their location within the page.

Abstract: A physical address extension feature maps multiple virtual memory spaces to an extended physical memory. A virtual space manager dynamically allocates pages of the physical memory to respective virtual spaces. The virtual space manager responds to a request from an application for allocation of a page of physical memory by returning a cookie indicating the allocated page. The virtual space manager responds to a request including the cookie by switching virtual address translation to the virtual memory space including the indicated page. The cookie is used to access a cookie cache of state information on the last page of virtual memory having been mapped into physical memory. For example, segments of the page store block map entries for snapshot copies, and the cookie cache caches the last-accessed values of the block numbers and their location within the page.