Abstract: Systems and methods for reducing communication latency are provided. A communication session with a remote device is initiated. One or more message packets are transmitted to the remote device. Subsequently, it is determined whether any additional message packet is scheduled to be transmitted to the remote device. In the event that no additional message packet is scheduled to be sent to the remote device, a loss detection packet is appended to a last message packet. The last message packet and the loss detection packet are transmitted to the remote device. It is further determined whether the last message packet was successfully received by the remote device based on receipt of an acknowledgment message. In the event that the last message packet was not successfully transmitted, a retransmit of the last message packet is executed.

Abstract: Systems and methods for reducing communication latency are provided. A communication session with a remote device is initiated. One or more message packets are transmitted to the remote device. Subsequently, it is determined whether any additional message packet is scheduled to be transmitted to the remote device. In the event that no additional message packet is scheduled to be sent to the remote device, a loss detection packet is appended to a last message packet. The last message packet and the loss detection packet are transmitted to the remote device. It is further determined whether the last message packet was successfully received by the remote device based on receipt of an acknowledgment message. In the event that the last message packet was not successfully transmitted, a retransmit of the last message packet is executed.

Abstract: Embodiments of the invention include systems and methods for providing block-level verification of replicated file systems. Embodiments operate in context of data storage environments, which may typically have multiple file systems, snapshots of file systems, and replicas of file systems. In one illustrative scenario, a replica is created of a file system having multiple associated snapshots, and a user desires to verify the accuracy of the replica. A signature is created for each of the source active file system and the target replica file system, so that each signature includes records of both block-level signatures and block-level allocations. The signatures are compared to discover any differences. The differences may then be reconciled, where possible, to determine whether the differences indicate a corrupt or otherwise invalid replica.

Abstract: The invention relates to a multiple QoS file system and methods of processing files at different QoS according to rules. The invention allocates multiple VLUNs at different qualities of service to the multiQoS file system. Using the rules, the file system chooses an initial QoS for a file when created. Thereafter, the file system moves files to different QoS using rules. Users of the file system see a single unified space of files, while administrators place files on storage with the new cost and performance according to attributes of the files. A multiQoS file system enhances the descriptive information for each file to contain the chosen QoS for the file.

Abstract: Embodiments of the invention include systems and methods for providing block-level verification of replicated file systems. Embodiments operate in context of data storage environments, which may typically have multiple file systems, snapshots of file systems, and replicas of file systems. In one illustrative scenario, a replica is created of a file system having multiple associated snapshots, and a user desires to verify the accuracy of the replica. A signature is created for each of the source active file system and the target replica file system, so that each signature includes records of both block-level signatures and block-level allocations. The signatures are compared to discover any differences. The differences may then be reconciled, where possible, to determine whether the differences indicate a corrupt or otherwise invalid replica.

Abstract: Embodiments of the invention include systems and methods for providing writable snapshot functionality for file systems. Pointer-based snapshots can be taken of an active version of the file system resulting in either (1) a read-only snapshot image and a new active version of the file system resulting from a read-only snapshot operation; or (2) a read-only snapshot image and two new active versions of the file system resulting from a writable snapshot operation. The two active file systems generated from writable snapshot operations are each independently and concurrently writable. Various techniques are also presented for handling multiple, concurrently active file systems. For example, novel techniques are described for allowing snapshot restore, compaction, and other functionality to operate in an environment having multiple read-only and writable versions of the file system.

Abstract: The invention relates to a multiple QoS file system and methods of processing files at different QoS. The file system allocates VLUNs and using rules chooses an initial QoS for a file when created and moves files to different QoS using rules. Users see a single unified space of files, while administrators place files on storage according to file attributes. A file system enhances the descriptive information for each file to contain the chosen QoS for the file. The invention classifies volumes (e.g., file systems or LUNs) according to application requirements and allocates space for volumes. An IT administrator configures volumes specifying size, type and priority. The host schedules I/O requests in priority queues using the volume definition to match applications and reduce seek time between volumes of different priorities. The data storage system therefore places data on the performance band of a storage device that best supports needs.

Abstract: The invention relates to methods for replicating a primary file system on a primary host to a secondary file system on a secondary host including determining a primary data block to replicate by reading a space map block entry (b, e) of the primary data block, wherein b represents the first snapshot and e the last snapshot to use the primary data block; computing a checksum of a primary data block and sending its number to the secondary host and determining a secondary data block that corresponds and computing its checksum then comparing the primary and secondary data block checksums and replicating the primary data block on the secondary file system when the primary and secondary checksums mismatch for the primary file system. In another aspect of the method if the primary and secondary checksums mismatch the method sends all data blocks from the primary file system allocated after a reliable snapshot on the secondary file system to the secondary host to be written on the secondary file system.

Abstract: Embodiments of the invention include systems and methods for providing writable snapshot functionality for file systems. Pointer-based snapshots can be taken of an active version of the file system resulting in either (1) a read-only snapshot image and a new active version of the file system resulting from a read-only snapshot operation; or (2) a read-only snapshot image and two new active versions of the file system resulting from a writable snapshot operation. The two active file systems generated from writable snapshot operations are each independently and concurrently writable. Various techniques are also presented for handling multiple, concurrently active file systems. For example, novel techniques are described for allowing snapshot restore, compaction, and other functionality to operate in an environment having multiple read-only and writable versions of the file system.

Abstract: The invention relates to methods for replicating a primary file system on a primary host to a secondary file system on a secondary host including determining a primary data block to replicate by reading a space map block entry (b, e) of the primary data block, wherein b represents the first snapshot and e the last snapshot to use the primary data block; computing a checksum of a primary data block and sending its number to the secondary host and determining a secondary data block that corresponds and computing its checksum then comparing the primary and secondary data block checksums and replicating the primary data block on the secondary file system when the primary and secondary checksums mismatch for the primary file system. In another aspect of the method if the primary and secondary checksums mismatch the method sends all data blocks from the primary file system allocated after a reliable snapshot on the secondary file system to the secondary host to be written on the secondary file system.

Abstract: The invention relates to a method of determining if a block was modified in a file system by comparing the versions of the base snapshot, the delta snapshot, and the space map block entry (b, e). In another aspect, the invention relates to a method of searching for blocks modified in a tree structured file system. The invention relates to methods and systems of snapshot management of a file system in a data storage system. To represent the snapshots, the invention maintains pointers to the root block pointer of each snapshot. When the active file system is modified, this invention avoids overwriting any blocks used by previous snapshots by allocating new blocks for the modified blocks. When the invention needs to put an established block in a new location, it must update a parent block to point to the new location. The update to the parent block may then require allocating a new block for the new parent block and so forth. Parts of the file system not modified since a snapshot remain in place.

Abstract: The invention relates to a method of determining if a block was modified in a file system by comparing the versions of the base snapshot, the delta snapshot, and the space map block entry (b, e). In another aspect, the invention relates to a method of searching for blocks modified in a tree structured file system. The invention relates to methods and systems of snapshot management of a file system in a data storage system. To represent the snapshots, the invention maintains pointers to the root block pointer of each snapshot. When the active file system is modified, this invention avoids overwriting any blocks used by previous snapshots by allocating new blocks for the modified blocks. When the invention needs to put an established block in a new location, it must update a parent block to point to the new location. The update to the parent block may then require allocating a new block for the new parent block and so forth. Parts of the file system not modified since a snapshot remain in place.

Abstract: The invention relates to a method of determining if a block was modified in a file system by comparing the versions of the base snapshot, the delta snapshot, and the space map block entry (b, e). In another aspect, the invention relates to a method of searching for blocks modified in a tree structured file system. The invention relates to methods and systems of snapshot management of a file system in a data storage system. To represent the snapshots, the invention maintains pointers to the root block pointer of each snapshot. When the active file system is modified, this invention avoids overwriting any blocks used by previous snapshots by allocating new blocks for the modified blocks. When the invention needs to put an established block in a new location, it must update a parent block to point to the new location. The update to the parent block may then require allocating a new block for the new parent block and so forth. Parts of the file system not modified since a snapshot remain in place.

Abstract: The present invention relates to systems and methods of asynchronous data replication. In an embodiment, the system includes a primary host that asynchronously transmits write and sync commands where each write and sync command includes a data set ID and a sequence number. A secondary host coupled to the primary host receives the write and sync commands out of order, tracks receipt of write and sync commands, and after receipt of the write and sync commands of the data set writes blocks associated with the write commands to data storage coupled to the secondary host.

Abstract: The present invention relates to methods and systems of snapshot management of a file system in a data storage system. To represent the snapshots, the invention maintains pointers to the root block pointer of each snapshot. When the active file system is modified, this invention avoids overwriting any blocks used by previous snapshots by allocating new blocks for the modified blocks. When the invention needs to put an established block in a new location, it must update a parent block to point to the new location. The update to the parent block may then require allocating a new block for the new parent block and so forth. Parts of the file system not modified since a snapshot remain in place. The amount of space required to represent snapshots scales with the fraction of the file system that users modify. To maintain snapshot integrity, this invention keeps track of the first and last snapshots that use each block in space map blocks spread throughout the file system data space.

Abstract: The invention relates to a multiple QoS file system and methods of processing files at different QoS. The file system allocates VLUNs and using rules chooses an initial QoS for a file when created and moves files to different QoS using rules. Users see a single unified space of files, while administrators place files on storage according to file attributes. A file system enhances the descriptive information for each file to contain the chosen QoS for the file. The invention classifies volumes (e.g., file systems or LUNs) according to application requirements and allocates space for volumes. An IT administrator configures volumes specifying size, type and priority. The host schedules I/O requests in priority queues using the volume definition to match applications and reduce seek time between volumes of different priorities. The data storage system therefore places data on the performance band of a storage device that best supports needs.

Abstract: The invention relates to a method of determining if a block was modified in a file system by comparing the versions of the base snapshot, the delta snapshot, and the space map block entry (b, e). In another aspect, the invention relates to a method of searching for blocks modified in a tree structured file system. The invention relates to methods and systems of snapshot management of a file system in a data storage system. To represent the snapshots, the invention maintains pointers to the root block pointer of each snapshot. When the active file system is modified, this invention avoids overwriting any blocks used by previous snapshots by allocating new blocks for the modified blocks. When the invention needs to put an established block in a new location, it must update a parent block to point to the new location. The update to the parent block may then require allocating a new block for the new parent block and so forth. Parts of the file system not modified since a snapshot remain in place.

Abstract: The invention relates to a multiple QoS file system and methods of processing files at different QoS according to rules. The invention allocates multiple VLUNs at different qualities of service to the multiQoS file system. Using the rules, the file system chooses an initial QoS for a file when created. Thereafter, the file system moves files to different QoS using rules. Users of the file system see a single unified space of files, while administration place files on storage with the new cost and performance according to attributes of the files. A multiQoS file system enhances the descriptive information for each file to contain the chosen QoS for the file.

Abstract: The invention relates to a multiple QoS file system and methods of processing files at different QoS according to rules. The invention allocates multiple VLUNs at different qualities of service to the multiQoS file system. Using the rules, the file system chooses an initial QoS for a file when created. Thereafter, the file system moves files to different QoS using rules. Users of the file system see a single unified space of files, while administrators place files on storage with the new cost and performance according to attributes of the files. A multiQoS file system enhances the descriptive information for each file to contain the chosen QoS for the file.

Abstract: The present invention relates to methods and systems of snapshot management of a file system in a data storage system. To represent the snapshots, the invention maintains pointers to the root block pointer of each snapshot. When the active file system is modified, this invention avoids overwriting any blocks used by previous snapshots by allocating new blocks for the modified blocks. When the invention needs to put an established block in a new location, it must update a parent block to point to the new location. The update to the parent block may then require allocating a new block for the new parent block and so forth. Parts of the file system not modified since a snapshot remain in place. The amount of space required to represent snapshots scales with the fraction of the file system that users modify. To maintain snapshot integrity, this invention keeps track of the first and last snapshots that use each block in space map blocks spread throughout the file system data space.