Abstract: A method for reducing duplicate data of an active file system, where the data is stored on a storage device of a storage system, is disclosed. A persistent image of the active file system is generated at a first point in time. At a later time, a sequence of steps to compare the active file system with the persistent image is initiated. Then, if a block of data of the active file system is identical to the data in the persistent image, the active file system is directed to refer to the persistent image for data of the file. Alternatively, if the block of data of the active file system is not identical to the data in the persistent image, the active file system is directed to refer to the data of the active file system. A file folding command may be issued to start the comparison.

Abstract: A write allocation technique extends a conventional write allocation procedure employed by a write anywhere file system of a storage system. A write allocator of the file system implements the extended write allocation technique in response to an event in the file system. The extended write allocation technique efficiently allocates blocks, and frees blocks, to and from a virtual volume (vvol) of an aggregate. The aggregate is a physical volume comprising one or more groups of disks, such as RAID groups, underlying one or more vvols of the storage system. The aggregate has its own physical volume block number (pvbn) space and maintains metadata, such as block allocation structures, within that pvbn space. Each vvol also has its own virtual volume block number (vvbn) space and maintains metadata, such as block allocation structures, within that vvbn space.

Abstract: A system and method for performing a distributed consistency check of a clustered file system. File system functions for loading an inode and/or buffer tree are modified so that in response to either of these functions being invoked, a consistency check is performed.

Abstract: A cloning technique enables efficient and substantially instantaneous creation of a clone that is a writable copy of a “parent” virtual volume (vvol) in an aggregate of a storage system. A base snapshot is provided from the parent vvol. In addition, a new vvol is created, along with a new file system identifier, a new subdirectory in the aggregate and a new storage label file. The new vvol is embodied as a clone and comprises an appropriately sized container file, wherein initially the container file has no data. Moreover, a volume information (volinfo) block for the clone is created that is a slightly modified version of the volinfo block from the base snapshot; the modified volinfo block is written to the container file. The clone is then instantiated by loading a file system associated with the new vvol onto the clone and bringing the clone “online”.

Abstract: A method and system for reallocating the data blocks of a logical data entity are described. According to one aspect of the invention, the physical arrangement of data blocks of a logical data entity are analyzed to determine a fragmentation level. Next the fragmentation level is compared with a fragmentation threshold previously assigned to the logical data entity. If the fragmentation level exceeds the fragmentation threshold, only those data blocks of the logical data entity that are within a predefined allocation area having a predetermined number of contiguous data blocks that are not associated with the logical data entity are reallocated.

Abstract: A file system layout apportions an underlying physical volume into one or more virtual volumes (vvols) of a storage system. The underlying physical volume is an aggregate comprising one or more groups of disks, such as RAID groups, of the storage system. The aggregate has its own physical volume block number (pvbn) space and maintains metadata, such as block allocation structures, within that pvbn space. Each vvol has its own virtual volume block number (vvbn) space and maintains metadata, such as block allocation structures, within that vvbn space. Notably, the block allocation structures of a vvol are sized to the vvol, and not to the underlying aggregate, to thereby allow operations that manage data served by the storage system (e.g., snapshot operations) to efficiently work over the vvols. The file system layout extends the file system layout of a conventional write anywhere file layout system implementation, yet maintains performance properties of the conventional implementation.

Abstract: A write allocation technique extends a conventional write allocation procedure employed by a write anywhere file system of a storage system. A write allocator of the file system implements the extended write allocation technique in response to an event in the file system. The extended write allocation technique efficiently allocates blocks, and frees blocks, to and from a virtual volume (vvol) of an aggregate. The aggregate is a physical volume comprising one or more groups of disks, such as RAID groups, underlying one or more vvols of the storage system. The aggregate has its own physical volume block number (pvbn) space and maintains metadata, such as block allocation structures, within that pvbn space. Each vvol also has its own virtual volume block number (vvbn) space and maintains metadata, such as block allocation structures, within that vvbn space.

Abstract: A system and method creates a writable clone of a read-only volume. A base snapshot is generated on a source volume on a source storage system and is duplicated as a read-only base snapshot replica on a target volume on a destination storage system. A copy (“clone) is then substantially instantaneously created from the read-only base snap-shot replica, thereby creating a writable clone of a read-only volume.

Abstract: A method for transferring data of a hybrid virtual volume of a computer data storage system from a source to a destination is disclosed. The method first translates intermingled virtual and physical volume block numbers of the hybrid virtual volume into a data stream having only virtual volume block numbers. The method then sends the data stream to a destination computer.

Abstract: An on-disk storage arrangement increases the number of persistent consistency point images (PCPIs) that may be maintained for a volume of a storage system. The on-disk storage arrangement comprises a novel volume information (volinfo) block representing a root of the volume; the volinfo block is stored at predefined locations on disk and comprises various system wide configuration data. The volinfo block further comprises a data structure configured to provide a level of indirection that increases the number of PCPIs maintainable by a file system executing on the storage system. To that end, the data structure may be organized as an array of pointers, wherein each pointer references a block containing a snapshot root, thereby enabling efficient access to each PCPI maintained by the file system.

Abstract: A system and method for enabling parallel replay of a backup memory log of client transaction request entries to a network storage appliance file system is provided. The backup memory is typically implemented as a non-volatile random access memory (NVRAM). An initiator establishes a swarm of messages with a plurality of transaction blocks pointing to logged request entries and related states associated therewith. The states represent the various phases of file system recovery and disk storage including a retrieval of disk information (data and meta-data), typically in the form of a LOAD, and a subsequent modify phase. The swarm is transferred to the file system for parallel disk information-retrieval in an interleaved process. Any transactions that cannot be performed due to a required prerequisite action (e.g. a prior file-create) are returned to the initiator for reloading once the prerequisite action has occurred.

Abstract: A technique converts a stream of virtual volume block numbers (vvbns) into a hybrid virtual volume (vvol) file system containing both physical volume block numbers (pvbns) and vvbns. The stream of vvbns is illustratively embodied as a file system data stream of a vvol that is transferred by a source to a destination in accordance with image transfer operations, such as volume copying and synchronous or asynchronous mirroring. Transfer of the vvol involves converting a file system on the source vvol into the file system data stream (i.e., a “pure” vvol stream), where all blocks of the vvol are represented by vvbns. The file system data stream is then transferred to the destination, where the vvbns of the pure vvol stream blocks are converted to pvbns of a hybrid stream.

Abstract: A technique translates a hybrid virtual volume (vvol) having a file system that contains intermingled virtual and physical volume block numbers (vbns) into a “pure” stream of virtual vbns (vvbns). The stream of vvbns is illustratively embodied as an output file system data stream of a vvol image that is transferred by a source storage system (“source”) to a destination storage system (“destination”) in accordance with image transfer operations, such as volume copying and synchronous or asynchronous mirroring, provided by a volume replication facility. The blocks that are sent as part of the image transfer are selected from a container file of the hybrid vvol on the source. In particular, the invention is directed to a technique for translating physical vbns (pvbns) of a source aggregate on the source to pure vvbns of the output file system data stream that can be used on a destination aggregate of the destination, where embedded pvbns in the source hybrid vvol image are not valid.

Abstract: An improved method and apparatus for creating a snapshot of a file system. A record of which blocks are being used by a snapshot is included in the snapshot itself, allowing effectively instantaneous snapshot creation and deletion. The state of the active file system is described by a set of metafiles; in particular, a bitmap (henceforth the “active map”) describes which blocks are free and which are in use. The inode file describes which blocks are used by each file, including the metafiles. The inode file itself is described by a special root inode, also known as the “fsinfo block”. The system begins creating a new snapshot by making a copy of the root inode. This copy of the root inode becomes the root of the snapshot.

Abstract: A file folding technique reduces the number of duplicate data blocks of a file consumed on a storage device of a file server configured to generate a persistent image of its active file system at a point in time. According to the file folding technique, if “old” data blocks of the file are over-written with “new” data and that new data is identical to the data of the persistent file image, the old data blocks are “freed” and the file is directed to refer to the persistent image for its data. The invention reduces disk space consumption in a file server configured to generate persistent images of its active file system and, in particular, reduces overall persistent image disk usage.

Abstract: The present invention provides a system and method for restoring a single file from a snapshot without the need to copy every individual block or inode from the snapshot. A file restore process duplicates the inode of a file within the active file system and performs a reconciliation process between the blocks of the twin inode and the snapshot inode. If the file does not exist within the active file system, a new buffer tree is created that points to the data blocks stored in the snapshot.

Abstract: In a system and method for updating a remote replicated destination file system snapshot with changes in a source file system snapshot, the snapshot being associated with a qtree (or other sub-organization of the file system volume), a qtree metadata file on the destination in provided. The qtree metadata file resides, in the destination volume, and outside the qtree structure. The metadata file stores state information with respect to each qtree. This metadata file resides at a known location in the destination volume. The metadata file can include a plurality of fixed length records having respective fields for storing various information including qtree-specific information, and can be part of a hidden metadata directory.

Abstract: A data storage system, such as RAID, upgraded dynamically including multiple stages, providing error checking data without taking the system off-line. Checksums are computed from the data and placed in block 63 of the same disk. The combination of parity bits across the parity disk, the remaining uncorrupted data in the data disks, and checksums within each disk includes sufficient information to enable restoration of corrupt data. The system is upgraded by reserving permanent checksum blocks, writing the checksums to a volume block number, and placing the checksums in permanently reserved checksum block locations after first moving data already there to unreserved blocks.

Abstract: An on-disk storage arrangement increases the number of persistent consistency point images (PCPIs) that may be maintained for a volume of a storage system. The on-disk storage arrangement comprises a novel volume information (volinfo) block representing a root of the volume; the volinfo block is stored at predefined locations on disk and comprises various system wide configuration data. The volinfo block further comprises a data structure configured to provide a level of indirection that increases the number of PCPIs maintainable by a file system executing on the storage system. To that end, the data structure may be organized as an array of pointers, wherein each pointer references a block containing a snapshot root, thereby enabling efficient access to each PCPI maintained by the file system.

Abstract: A defragmentation technique determines the extent to which data blocks of a file are fragmented on disks of a computer and, in response, efficiently relocates those blocks if such relocation improves the on-disk layout of the file. Each indirect block of the file is examined and the current layout of the range of pointers referencing the data blocks is determined. In addition, the number of operations needed to retrieve those data blocks from disks is calculated. A potential new layout is then estimated based on an average fullness of the file system. If the potential new layout improves the fragmentation of the current layout, then the data blocks for that range are relocated, if there is sufficient free space on disk. Otherwise, the blocks are not relocated and the current on-disk layout of the file is maintained.