Abstract: Information on strides configured in the second cache includes information indicating a number of valid tracks in the strides, wherein a stride has at least one of valid tracks and free tracks not including valid data. A determination is made of tracks to demote from the first cache. A first stride is formed including the determined tracks to demote. The tracks from the first stride are added to a second stride in the second cache that has no valid tracks. A target stride in the second cache is selected based on a stride most recently used to consolidate strides from at least two strides into one stride. Data from the valid tracks is copied from at least two source strides in the second cache to the target stride.

Abstract: Destage grouping of tracks is restricted to a bottom portion of a least recently used (LRU) list without grouping the tracks at a most recently used end of the LRU list to avoid the destaging conflicts. The destage grouping of tracks is destaged from the bottom portion of the LRU list.

Abstract: Mechanisms for managing data segments in a tiered storage system are provided. The mechanisms maintain at least one counter for each data segment in the tiered storage system. Each counter in the at least one counter counts a number of access operations to a corresponding data segment for a predetermined time interval. The mechanisms further perform one or more analytical operations based on one or more values of the at least one counter for each data segment to make residence determinations for each data segment. The mechanisms also adjust a storage location of one or more data segments in tiers of the tiered storage system to thereby move the one or more data segments to appropriate tiers of the tiered storage system based on results of the one or more analytical operations.

Abstract: In one aspect of the present description, at least one of the value of a prestage trigger and the value of the prestage amount, may be modified as a function of the drive speed of the storage drive from which the units of read data are prestaged into a cache memory. Thus, cache prestaging operations in accordance with another aspect of the present description may take into account storage devices of varying speeds and bandwidths for purposes of modifying a prestage trigger and the prestage amount. Other features and aspects may be realized, depending upon the particular application.

Abstract: Tracks are selected for destaging from a least recently used (LRU) list and the selected tracks are moved to a destaging wait list. The selected tracks are grouped and destaged from the destaging wait list.

Abstract: Provided are a computer program product, system, and method for populating strides of tracks to demote from a first cache to a second cache. A first cache maintains modified and unmodified tracks from a storage system subject to Input/Output (I/O) requests. A determination is made to demote tracks from the first cache. A determination is made as to whether there are enough tracks ready to demote to form a stride, wherein tracks are written to a second cache in strides defined for a Redundant Array of Independent Disk (RAID) configuration. A stride is populated with tracks ready to demote in response to determining that there are enough tracks ready to demote to form the stride. The stride of tracks, to demote from the first cache, are promoted to the second cache. The tracks in the second cache that are modified are destaged to the storage system.

Abstract: A storage controller that includes a cache, receives a command from a host, wherein a set of criteria corresponding to read response times for executing the command have to be satisfied. A destage application that destages tracks based at least on recency of usage and spatial location of the tracks is executed, wherein a spatial ordering of the tracks is maintained in a data structure, and the destage application traverses the spatial ordering of the tracks. Tracks are destaged from at least inside or outside diameters of disks at periodic intervals, while traversing the spatial ordering of the tracks, wherein the set of criteria corresponding to the read response times for executing the command are satisfied.

Abstract: For a plurality of input/output (I/O) operations waiting to assemble complete data tracks from data segments, a process, separate from a process responsible for the data assembly into the complete data tracks, is initiated for waking a predetermined number of the waiting I/O operations. A total number of I/O operations to be awoken at each of an iterated instance of the waking is limited.

Abstract: Information is maintained on strides configured in a second cache and occupancy counts for the strides indicating an extent to which the strides are populated with valid tracks and invalid tracks. A determination is made of tracks to demote from a first cache. A first stride is formed including the determined tracks to demote. The tracks from the first stride are to a second stride in the second cache having an occupancy count indicating the stride is empty. A determination is made of a target stride in the second cache based on the occupancy counts of the strides in the second cache. A determination is made of at least two source strides in the second cache having valid tracks based on the occupancy counts of the strides in the second cache. The target stride is populated with the valid tracks from the source strides.

Abstract: Provided is a method for processing a read operation for a target block of data. A read operation for the target block of data in target storage is received, wherein the target block of data is in an instant virtual copy relationship with a source block of data in source storage. It is determined that the target block of data in the target storage is not consistent with the source block of data in the source storage. The source block of data is retrieved. The data in the source block of data in the cache is synthesized to make the data appear to be retrieved from the target storage. The target block of data is marked as read from the source storage. In response to the read operation completing, the target block of data that was read from the source storage is demoted.

Abstract: Provided are a computer program product, system, and method for processing a read operation for a target block of data. A read operation for the target block of data in target storage is received, wherein the target block of data is in an instant virtual copy relationship with a source block of data in source storage. It is determined that the target block of data in the target storage is not consistent with the source block of data in the source storage. The source block of data is retrieved. The data in the source block of data in the cache is synthesized to make the data appear to be retrieved from the target storage. The target block of data is marked as read from the source storage. In response to the read operation completing, the target block of data that was read from the source storage is demoted.

Abstract: Provided are a computer program product, system, and method for handling high priority requests in a sequential access storage device. Received modified tracks for write requests are cached in a non-volatile storage device integrated with the sequential access storage device. A destage request is added to a request queue for a received write request having modified tracks for the sequential access storage medium cached in the non-volatile storage device. A read request indicting a priority is received. A determination is made of a priority of the read request as having a first priority or a second priority. The read request is added to the request queue in response to determining that the determined priority is the first priority. The read request is processed at a higher priority than the read and destage requests in the request queue in response to determining that the determined priority is the second priority.

Abstract: Information is maintained on strides configured in a second cache and occupancy counts for the strides indicating an extent to which the strides are populated with valid tracks and invalid tracks. A determination is made of tracks to demote from a first cache. A first stride is formed including the determined tracks to demote. The tracks from the first stride are to a second stride in the second cache having an occupancy count indicating the stride is empty. A determination is made of a target stride in the second cache based on the occupancy counts of the strides in the second cache. A determination is made of at least two source strides in the second cache having valid tracks based on the occupancy counts of the strides in the second cache. The target stride is populated with the valid tracks from the source strides.

Abstract: Information on strides configured in the second cache includes information indicating a number of valid tracks in the strides, wherein a stride has at least one of valid tracks and free tracks not including valid data. A determination is made of tracks to demote from the first cache. A first stride is formed including the determined tracks to demote. The tracks from the first stride are added to a second stride in the second cache that has no valid tracks. A target stride in the second cache is selected based on a stride most recently used to consolidate strides from at least two strides into one stride. Data from the valid tracks is copied from at least two source strides in the second cache to the target stride.

Abstract: Provided are a computer program product, system, and method for populating strides of tracks to demote from a first cache to a second cache. A first cache maintains modified and unmodified tracks from a storage system subject to Input/Output (I/O) requests. A determination is made to demote tracks from the first cache. A determination is made as to whether there are enough tracks ready to demote to form a stride, wherein tracks are written to a second cache in strides defined for a Redundant Array of Independent Disk (RAID) configuration. A stride is populated with tracks ready to demote in response to determining that there are enough tracks ready to demote to form the stride. The stride of tracks, to demote from the first cache, are promoted to the second cache. The tracks in the second cache that are modified are destaged to the storage system.

Abstract: Information on strides configured in the second cache includes information indicating a number of valid tracks in the strides, wherein a stride has at least one of valid tracks and free tracks not including valid data. A determination is made of tracks to demote from the first cache. A first stride is formed including the determined tracks to demote. The tracks from the first stride are added to a second stride in the second cache that has no valid tracks. A target stride in the second cache is selected based on a stride most recently used to consolidate strides from at least two strides into one stride. Data from the valid tracks is copied from at least two source strides in the second cache to the target stride.

Abstract: A set of logical extents, each having compressed logical tracks of data, is mapped to a head physical extent and, if the head physical extent is determined to have been filled, to at least one overflow extent having spatial proximity to the head physical extent. Pursuant to at least one subsequent write operation and destage operation, the at least one subsequent write operation and destage operation determined to be associated with the head physical extent, the write operation is mapped to one of the head physical extent, the at least one overflow extent, and an additional extent having spatial proximity to the at least one overflow extent.

Abstract: A storage controller that includes a cache, receives a command from a host, wherein a set of criteria corresponding to read response times for executing the command have to be satisfied. A destage application that destages tracks based at least on recency of usage and spatial location of the tracks is executed, wherein a spatial ordering of the tracks is maintained in a data structure, and the destage application traverses the spatial ordering of the tracks. Tracks are destaged from at least inside or outside diameters of disks at periodic intervals, while traversing the spatial ordering of the tracks, wherein the set of criteria corresponding to the read response times for executing the command are satisfied.

Abstract: Provided are a computer program product, system, and method for managing track discard requests to include in discard track messages. A backup copy of a track in a cache is maintained in the cache backup device. A track discard request is generated to discard tracks in the cache backup device removed from the cache. Track discard requests are queued in a discard track queue. In response to detecting that a predetermined number of track discard requests are queued in the discard track queue while processing in a discard multi-track mode, one discard multiple tracks message is sent indicating the tracks indicated in the queued predetermined number of track discard requests to the cache backup device instructing the cache backup device to discard the tracks indicated in the discard multiple tracks message. In response to determining a predetermined number of periods of inactivity while processing in the discard multi-track mode, processing the track discard requests is switched to a discard single track mode.

Abstract: A disk drive receives a request to write at least one block of a first block size, wherein the disk drive is configured to store blocks of a second block size that is larger in size than the first block size, and wherein the disk drive stores via emulation a plurality of emulated blocks of the first block size in each block of the second block size. The disk drive generates a read error, in response to reading a selected block of the second block size in which the at least block of the first block size is to be written via the emulation. The disk drive performs a destructive write of selected emulated blocks of the first block size that caused the read error to be generated. The disk drive writes the at least one block of the first block size in the selected block of the second block size. The disk drive sends a notification to indicate the performing of the destructive write.