Abstract: The present invention provides a method for reducing rebuild time on a Redundant Array of Independent Disks (RAID) device. A first stripe of the RAID device is selected. Write-back caching on a drive being built is enabled. Data and/or parity may be read from at least one other drive. The at least one other drive and the drive being built belong to a same stripe of the RAID device. When a RAID level of the RAID device is 5, the at least one of data or parity is XORed (exclusive ORed) to obtain a result. When the RAID level of the RAID device is 1, the at least one of data or parity is data and treated as the result. The result is written to a second drive, which is a repaired, replaced, or hot-spare drive for the drive being built.

Abstract: A method for reading data from a data storage system is provided. The method comprises requesting a virtual data volume to access data from one or more data blocks in the data storage system; requesting a virtual protection information volume to access protection information associated with the data blocks; validating the data using the protection information; and providing the data to the host interface, in response to successful validation of the data. A method for writing data to a data storage system is also provided. The method comprises receiving data to be written to one or more data blocks in the data storage system, wherein the data is stored in a cache; generating protection information to be stored on a virtual protection information volume; requesting a virtual data volume to update the data blocks with the data; and requesting the virtual protection information volume to store the protection information.

Abstract: A method for validating data in a data storage system comprising associating a first data chunk with first check data and storing the first data chunk and the first check data on a first storage device. Additional associated data chunks of the first data and associated additional check data are stored on at least one of the first storage device or one or more additional storage devices. At least a portion of the first check data and at least a portion of the additional check data are stored to a second storage device, which is distinct from the first storage device and the additional storage devices. I/O access to the second storage device is minimized by retaining at least a portion of the first check data and at least a portion of the additional check data in a readily accessible storage medium, during servicing of a first I/O request.

Abstract: Methods and associated structures for utilizing write-back cache management modes for local cache memory of disk drives coupled to a storage controller while maintaining data integrity of the data transferred to the local cache memories of affected disk drives. In one aspect hereof, a state machine model of managing cache blocks in a storage controller cache memory maintains blocks in the storage controller's cache memory in a new state until verification is sensed that the blocks have been successfully stored on the persistent storage media of the affected disk drives. Responsive to failure or other reset of the disk drive, the written cache blocks may be re-written from the copy maintained in the cache memory of the storage controller. In another aspect, an alternate controller's cache memory may also be used to mirror the cache blocks from the primary storage controller's cache memory as additional data integrity assurance.

Abstract: Methods and associated structures for utilizing write-back cache management modes for local cache memory of disk drives coupled to a storage controller while maintaining data integrity of the data transferred to the local cache memories of affected disk drives. In one aspect hereof, a state machine model of managing cache blocks in a storage controller cache memory maintains blocks in the storage controller's cache memory in a new state until verification is sensed that the blocks have been successfully stored on the persistent storage media of the affected disk drives. Responsive to failure or other reset of the disk drive, the written cache blocks may be re-written from the copy maintained in the cache memory of the storage controller. In another aspect, an alternate controller's cache memory may also be used to mirror the cache blocks from the primary storage controller's cache memory as additional data integrity assurance.

Abstract: A method for returning a logical volume which is part of a redundant data storage system to on-line status following a disk failure within the logical volume during the time when another of that volume's disks is unavailable as a result of having its firmware updated, as an example. Data which would otherwise be changed in the logical volume due to host write requests is directed to a logging facility within the data storage system, but outside of the logical volume undergoing upgrade.

Abstract: Disclosed is a method for continuing a rebuilding process of a RAID system by flagging a block of data as being bad when a media error or other error occurs that prohibits the reconstruction of data. The block of data may be flagged by writing a bad error correction code to the block of data, by keeping a log of bad blocks of data, or by otherwise indicating that the block of data is known bad.

Abstract: Disclosed is a method for continuing a write operation in a RAID device when parity cannot be generated. In cases where a read error or plurality of read errors prohibits the proper calculation of parity for a block of data, the parity block may be written as a bad block of data for subsequent read operations. The parity block may be forced to be a bad block of data by writing a recognizable pattern of data with a known bad error correction code or other method of forcing a read error to occur on an otherwise good block of a disk storage device. This method allows the write operation to continue without halting the system as with conventional RAID devices.

Abstract: A method for reducing data/parity inconsistencies due to a storage controller failure in computer storage systems with dual, independent storage controllers and a number of logical volumes comprising one or more physical disk drive devices includes recognizing a failure of the storage controller; assuming access control of the volume; and thereafter, performing at least one write to the volume, wherein, for a predetermined number of writes (N) to the volume after failure of the storage controller, new parity is calculated for the write using new data and other data (Method 2). The predetermined number of writes (N) is at least equal to or greater than the queue depth of the failed storage controller (i.e., the number of I/O operations that the failed storage controller may service at a given time. The method may be implemented by each storage controller of the computer storage system.

Abstract: In a computerized data storage system, when data is to be updated in a primary, or “base,” logical volume, a snapshot volume is formed from the base volume. The updates are then made to the snapshot volume, preferably while the base volume is still used to satisfy normal I/O (input/output) access requests. After the updating is complete, the snapshot volume is rolled back into the base volume. During the rollback, any remaining original data in the base volume and the updated data in either the base volume or snapshot volume are available for satisfying the normal I/O access requests. Thus, the updating appears to be instantaneous, since the entire updated data is immediately available upon starting the rollback.

Abstract: A method for providing sequential initialization of redundancy data in a volume comprising the steps of: (A) defining a boundary; (B) determining a location of the data with respect to the boundary; and (C) initializing a redundancy location of the volume and writing the data and a redundancy of the data to the volume.

Abstract: In a computerized data storage system, snapshot volumes are used to preserve the state of the base volume at various points in time, and later-formed snapshot volumes are retained after rolling back an earlier-formed snapshot volume into the base volume. During the rollback, data writes to the base volume are copied to the later-formed snapshot volumes when necessary to continue to preserve the states of the base volume represented by the later-formed snapshot volumes.

Abstract: The present invention is directed to a method of recovering a write ahead log after an interruption. In a first aspect of the present invention, a method of writing a log entry of a write ahead log may include initiating a log write to a write ahead log, the write ahead log having a first sector, and a second sector, wherein the first sector is followed by the second sector. A log entry including a sequence number is written to the second sector. Then, the log entry including the sequence number is written to the first sector.

Abstract: Disclosed is a method for continuing a write operation in a RAID device when parity cannot be generated. In cases where a read error or plurality of read errors prohibits the proper calculation of parity for a block of data, the parity block may be written as a bad block of data for subsequent read operations. The parity block may be forced to be a bad block of data by writing a recognizable pattern of data with a known bad error correction code or other method of forcing a read error to occur on an otherwise good block of a disk storage device. This method allows the write operation to continue without halting the system as with conventional RAID devices.

Abstract: The present invention is directed to a method and system for expanding volume capacity. A method of expanding volume capacity on a storage device may include receiving a request to expand capacity of a target volume by a requested amount. A first hierarchy is queried for unused capacity, wherein if unused capacity is at least one of greater than or equal to the requested amount, the unused capacity is positioned within the target volume. If unused capacity is less than the requested amount, at least one successive hierarchy is queried to locate unused capacity, which is at least one of greater than or equal to the requested amount, the successive hierarchy located at a logic block address further from a target volume logic block address than a first hierarchy logic block address. The unused capacity is then positioned to be included with the target volume.

Abstract: The present invention is directed to a system and method for reading and writing N-way mirrored storage devices. A method of reading data in a data storage system, where the data storage system may include a first data storage device, a second data storage device and a third data storage device, is provided. A first item of data is read from a first data storage device, a second item of data is read from a second data storage device, and a third item of data is read from a third storage device. The first item of data from the first storage device is compared with the second item of data from the second storage device and the third item of data from the third storage device. If the first item of data matches at least one of the second item of data and the third item of data, the first item of data is valid. If the first item of data does not match at least one of the second item of data and the third item of data, the second item of data is valid.

Abstract: Block-level storage is managed in a computerized storage system by recording into a write-ahead log a description of block-level updates made to data in a volume in a main memory and in a storage device of the computerized storage system. The write-ahead logging enables directory updates for each block-level write request to be logged, so the write request can be allowed to complete independently of other write requests.

Abstract: A data storage system and a method of managing data in the storage system. A method of performing a write to a data storage system, including a first storage device and a second storage device, may include writing a first set of header information to a first storage device and a second storage device. The first set of header information includes a first sequence number and a second sequence number, in which the first set of header information includes a first sequence number incremented to indicate a change from the second sequence number. The method may also include returning status of completion of writing the second set of header information. Invalid data or an interruption may also be detected by examining the first and second sequence numbers. Data is written to the first storage device and the second storage device. Then, a second set of header information is written to a first storage device and a second storage device.

Abstract: Disclosed is a method for continuing a rebuilding process of a RAID system by flagging a block of data as being bad when a media error or other error occurs that prohibits the reconstruction of data. The block of data may be flagged by writing a bad error correction code to the block of data, by keeping a log of bad blocks of data, or by otherwise indicating that the block of data is known bad.

Abstract: A method for reducing data/parity inconsistencies due to a storage controller failure in computer storage systems with dual, independent storage controllers and a number of logical volumes comprising one or more physical disk drive devices includes recognizing a failure of the storage controller; assuming access control of the volume; and thereafter, performing at least one write to the volume, wherein, for a predetermined number of writes (N) to the volume after failure of the storage controller, new parity is calculated for the write using new data and other data (Method 2). The predetermined number of writes (N) is at least equal to or greater than the queue depth of the failed storage controller (i.e., the number of I/O operations that the failed storage controller may service at a given time. The method may be implemented by each storage controller of the computer storage system.