Abstract: When parity checking in a disk array such as a RAID-6 system determines data and parity information is unsynchronized, additional calculations are performed to determine whether the error may be attributed to faulty data on a disk drive or to a more systemic problem such as a faulty controller. In particular, for each particular error detected, the parity generating information is analyzed to determine if each error involves a common disk index. If so, the data can be corrected on that disk; if not other corrective procedures are implemented.

Abstract: A method, computer program product and system for dynamically optimizing the limit and the thresholds of a write cache for a storage adapter connected to storage devices, includes measuring continually an overall locality of data in the write cache for the storage devices, calculating the limit of the write cache dynamically for each storage device using the overall locality and a device-related information, and calculating the threshold of the write cache dynamically for each storage device by combining a fair amount and a device-related additional amount.

Abstract: A method, computer program product and computer system for maintaining write cache and parity update footprint coherency in a multiple storage adaptor configuration for storage adaptors in a storage subsystem, which includes providing atomic updating of the storage adaptors and the attached disk drives, enabling runtime addition and runtime subtraction of a storage adaptor in the multiple storage adaptor configuration, and maintaining write cache and parity update footprint coherency using atomic updating, runtime addition and runtime subtraction of a storage adaptor.

Abstract: When parity checking in a disk array such as a RAID-6 system determines data and parity information is unsynchronized, additional calculations are performed to determine whether the error may be attributed to faulty data on a disk drive or to a more systemic problem such as a faulty controller. In particular, for each particular error detected, the parity generating information is analyzed to determine if each error involves a common disk index. If so, the data can be corrected on that disk; if not other corrective procedures are implemented.

Abstract: In a disk array environment such as a Redundant Array of Independent Disks-6 (RAID-6) environment, the overall performance overhead associated with exposed mode operations such as resynchronization, rebuild and exposed mode read operations is reduced through increased parallelism. By selecting only subsets of the possible disks required to solve a parity stripe equation for a particular parity stripe, accesses to one or more disks in a disk array may be omitted, thus freeing the omitted disks to perform other disk accesses. In addition, disk accesses associated with different parity stripes may be overlapped such that the retrieval of data necessary for restoring data for one parity stripe is performed concurrently with the storage of restored data for another parity stripe.

Abstract: A method, computer program product and computer system for maintaining write cache and parity update footprint coherency in a multiple storage adaptor configuration for storage adaptors in a storage subsystem, which includes providing atomic updating of the storage adaptors and the attached disk drives, enabling runtime addition and runtime subtraction of a storage adaptor in the multiple storage adaptor configuration, and maintaining write cache and parity update footprint coherency using atomic updating, runtime addition and runtime subtraction of a storage adaptor.

Abstract: A method, computer program product and system for dynamically optimizing the limit and the thresholds of a write cache for a storage adapter connected to storage devices, includes measuring continually an overall locality of data in the write cache for the storage devices, calculating the limit of the write cache dynamically for each storage device using the overall locality and a device-related information, and calculating the threshold of the write cache dynamically for each storage device by combining a fair amount and a device-related additional amount.

Abstract: Data associated with the state of a parity update operation in a disk array system such as a RAID-6 system is stored during performance of the operation so that, in the event the operation is interrupted, recovery may be initiated using the stored data. The stored data may include a state indicator that is indicative of the status of the parity update operation, and snapshot data (e.g., a delta value indicative of a difference between new and old data) captured during the parity update operation.

Abstract: When parity checking in a disk array such as a RAID-6 system determines data and parity information is unsynchronized, additional calculations are performed to determine whether the error may be attributed to faulty data on a disk drive or to a more systemic problem such as a faulty controller. In particular, for each particular error detected, the parity generating information is analyzed to determine if each error involves a common disk index. If so, the data can be corrected on that disk; if not other corrective procedures are implemented.

Abstract: When parity checking in a disk array such as a RAID-6 system determines data and parity information is unsynchronized, additional calculations are performed to determine whether the error may be attributed to faulty data on a disk drive or to a more systemic problem such as a faulty controller. In particular, for each particular error detected, the parity generating information is analyzed to determine if each error involves a common disk index. If so, the data can be corrected on that disk; if not other corrective procedures are implemented.

Abstract: Data associated with the state of a parity update operation in a disk array system such as a RAID-6 system is stored during performance of the operation so that, in the event the operation is interrupted, recovery may be initiated using the stored data. The stored data may include a state indicator that is indicative of the status of the parity update operation, and snapshot data (e.g., a delta value indicative of a difference between new and old data) captured during the parity update operation.

Abstract: Data associated with the state of a parity update operation in a disk array system such as a RAID-6 system is stored during performance of the operation so that, in the event the operation is interrupted, recovery may be initiated using the stored data. The stored data may include a state indicator that is indicative of the status of the parity update operation, and snapshot data (e.g., a delta value indicative of a difference between new and old data) captured during the parity update operation.

Abstract: When parity checking in a disk array such as a RAID-6 system determines data and parity information is unsynchronized, additional calculations are performed to determine whether the error may be attributed to faulty data on a disk drive or to a more systemic problem such as a faulty controller. In particular, for each particular error detected, the parity generating information is analyzed to determine if each error involves a common disk index. If so, the data can be corrected on that disk; if not other corrective procedures are implemented.

Abstract: During a parity update of a parity stripe in a disk array, constant values used in finite field arithmetic are algebraically combined in order to reduce the number of buffers and steps needed to update multiple parity values when a change in data occurs. In one implementation, for example, the contents of a buffer that stores the product of a delta value associated with the change in data and a first constant, which is used to update a first parity value, are multiplied by a value representative of the ratio of a second constant, which is used to update a second parity value, and the first constant.

Abstract: In a first aspect, a method is provided for updating a compressed cache. The method includes the steps of (1) initiating an update routine for replacing first data stored within the cache with second data, wherein a first section of a compressed data band stored in the cache includes the first data and a second section of the compressed data band includes third data; and (2) in response to initiating the update routine, replacing the first data within the compressed data band with the second data without decompressing the third data. Numerous other aspects are provided.

Abstract: In a first aspect, a method is provided for updating a compressed cache. The method includes the steps of (1) initiating an update routine for replacing first data stored within the cache with second data, wherein a first section of a compressed data band stored in the cache includes the first data and a second section of the compressed data band includes third data; and (2) in response to initiating the update routine, replacing the first data within the compressed data band with the second data without decompressing the third data. Numerous other aspects are provided.