Abstract: Provided are a method, system, and article of manufacture for copying data from a first cluster to a second cluster to reassign storage areas from the first cluster to the second cluster. An operation is initiated to reassign storage areas from a first cluster to a second cluster, wherein the first cluster includes a first cache and a first storage unit and the second cluster includes a second cache and a second storage unit. Data in the first cache for the storage areas to reassign to the second cluster is copied to the second cache. Data in the first storage unit for storage areas remaining assigned to the first cluster is copied to the second storage unit.

Abstract: Provided are a method, system, and article of manufacture for determining modified data in cache for use during a recovery operation. An event is detected during which processing of writes to a storage device is suspended. A cache including modified data not destaged to the storage device is scanned to determine the data units having modified data in response to detecting the event. The data units having the modified data is indicated in a backup storage. The indication of the data units having the modified data in the backup storage is used during a recovery operation.

Abstract: In a data storage subsystem with disk storage and a pair of clusters, one set of DASD fast write data is in cache of one cluster and in non-volatile data storage of the other. In response to a failover of one of the pair of clusters to a local cluster, the local cluster converts the DASD fast write data in local cache to converted fast write data to prioritize the converted data for destaging to disk storage. In response to failure to destage, the local cluster allocates local non-volatile storage tracks and emulates a host adapter to store the converted fast write data by the local non-volatile storage, reconverting the converted fast write data of the non-volatile storage to local DASD fast write data stored in the local non-volatile storage and stored in the local cache storage.

Abstract: An apparatus, system, and method are disclosed for migrating wear spots in solid-state drives. A count module counts lifetime write cycles for logical units of a plurality of solid-state memories. Each logical unit has a logical address. An identification module identifies a wear spot on a first logical unit of a first solid-state memory if a count for the first logical unit exceeds a cycle threshold. A migration module dynamically migrates data of the first logical unit to a second solid-state memory, wherein the data is continuously available at an original logical address.

Abstract: A method, system, and computer program product for preserving data in a storage subsystem having dual cache and dual nonvolatile storage (NVS) through a failover from a failed cluster to a surviving cluster is provided. A memory preserved indicator is initiated to mark tracks on a cache of the surviving cluster to be preserved, the tracks having an image in an NVS of the failed cluster. A destage operation is performed to destage the marked tracks. Subsequent to a determination that each of the marked tracks have been destaged, the memory preserved indicator is disabled to remove the mark from the tracks. If the surviving cluster reboots previous to each of the marked tracks having been destaged, the cache is verified as a memory preserved cache, the marked tracks are retained for processing while all unmarked tracks are removed, and the marked tracks are processed.

Abstract: A method, system and computer program product for preserving data in a storage subsystem having dual cache and dual nonvolatile storage (NVS) through a failover from a failed cluster to a surviving cluster, the surviving cluster undergoing a rebooting process, is provided. A memory preserved indicator associated with a cache of the surviving cluster is detected. The memory preserved indicator designates marked tracks having an image in an NVS of the failed cluster to be preserved through the rebooting process. A counter in a data structure of the surviving cache is incremented. If a value of the counter exceeds a predetermined value, a cache memory is initialized, and the marked tracks are removed from the cache to prevent an instance of repetitive reboots caused by a corrupted structure in the cache memory.

Abstract: An apparatus, system, and method are disclosed for preventing write starvation in a storage controller with access to low performance storage devices. A storage device allocation module is included to assign a storage device write cache limit for each storage device accessible to a storage controller. The storage device write cache limit comprises a maximum amount of write cache of the storage controller available to a storage device for a write operation. At least one storage device comprises a low performance storage device and a total amount of storage available to the storage devices comprises an amount greater than a total storage capacity of the write cache. A low performance write cache limit module is included to set a low performance write cache limit. The low performance write cache limit comprises an amount of write cache available for use by the at least one low performance storage device for a write operation.

Abstract: An apparatus, system, and method are disclosed for relocating storage pool hot spots. An identification module identifies a hot spot on a first storage pool if accesses to the first storage pool exceed an access threshold. The first storage pool is part of a plurality of storage pools. Each storage pool comprises a plurality of logical segments from a plurality of storage devices. Each storage device is of a specified class. A migration module dynamically migrates data of a first logical segment to a second storage pool. The migration is transparent to a host and the data of the first logical segment is continuously available to the host.

Abstract: An apparatus, system, and method are disclosed for relocating logical array hot spots. An organization module organizes a plurality of logical arrays. Each logical array comprises a plurality of logical segments from a plurality of storage devices and configured to store data. An identification module identifies a hot spot on a first logical array if accesses to the first logical array exceed an access threshold. A migration module dynamically migrates a first logical segment from the first logical array to a second logical segment of a second logical array, wherein the migration is transparent to a host and data of the first logical segment is continuously available to the host.

Abstract: Provided are a method, system, and program for managing write processes in which a list of destination location identifiers for pending write operations is maintained in an array having an array pointer which identifies the next available entry of the array. In one embodiment, the array includes a stack of variable size. Adding a destination location identifier of a pending write operation increases the size of the stack. Removing a destination location identifier of a completed write operation reduces the size of the stack. A stack index may be incremented as write operation destination location identifiers are added and may be decremented as write operation destination location identifiers are removed from the stack.

Abstract: Provided are a method, system, and program for managing write processes in which a list of destination location identifiers for pending write operations is maintained in an array having an array pointer which identifies the next available entry of the array. In one embodiment, the array includes a stack of variable size. Adding a destination location identifier of a pending write operation increases the size of the stack. Removing a destination location identifier of a completed write operation reduces the size of the stack. A stack index may be incremented as write operation destination location identifiers are added and may be decremented as write operation destination location identifiers are removed from the stack.

Abstract: Non volatile storage may be employed to temporarily store data which is destaged to data storage drives. The non volatile storage is configured to preserve the data through a power outage. Some data may be preserved, but is not needed, such as the result of a failover to another non volatile storage. This unneeded data is tested to verify the non volatile storage by indicating whether the data survived the power cycle from full power to self refresh mode battery power to full power, without risking the loss of data that is needed.

Abstract: Provided are a method, system, and article of manufacture for copying data from a first cluster to a second cluster to reassign storage areas from the first cluster to the second cluster. An operation is initiated to reassign storage areas from a first cluster to a second cluster, wherein the first cluster includes a first cache and a first storage unit and the second cluster includes a second cache and a second storage unit. Data in the first cache for the storage areas to reassign to the second cluster is copied to the second cache. Data in the first storage unit for storage areas remaining assigned to the first cluster is copied to the second storage unit.

Abstract: In a data storage subsystem with disk storage and a pair of clusters, one set of DASD fast write data is in cache of one cluster and in non-volatile data storage of the other. In response to a failover of one of the pair of clusters to a local cluster, the local cluster converts the DASD fast write data in local cache to converted fast write data to prioritize the converted data for destaging to disk storage. In response to failure to destage, the local cluster allocates local non-volatile storage tracks and emulates a host adapter to store the converted fast write data by the local non-volatile storage, reconverting the converted fast write data of the non-volatile storage to local DASD fast write data stored in the local non-volatile storage and stored in the local cache storage.

Abstract: An apparatus, system, and method are disclosed for preventing write starvation in a storage controller with access to low performance storage devices. A storage device allocation module is included to assign a storage device write cache limit for each storage device accessible to a storage controller. The storage device write cache limit comprises a maximum amount of write cache of the storage controller available to a storage device for a write operation. At least one storage device comprises a low performance storage device and a total amount of storage available to the storage devices comprises an amount greater than a total storage capacity of the write cache. A low performance write cache limit module is included to set a low performance write cache limit. The low performance write cache limit comprises an amount of write cache available for use by the at least one low performance storage device for a write operation.

Abstract: Provided are a method, system, and an article of manufacture for preventing data loss. Modified data is stored in a volatile storage. The stored modified data is copied onto a non-volatile storage. A determination is made as to whether the non-volatile storage should be checked for errors. In certain implementations, on determining that the nonvolatile storage should be checked for errors the non-volatile storage is checked for errors. If on checking the non-volatile storage is found to have an error, an indication of the error is provided.

Abstract: Provided are a method, system, and program for maintaining data in a first cache and second cache, wherein a backup cache maintains a backup copy of data in the first cache, and wherein the first cache is used to cache a first set of data in a storage system and the second cache is used to cache a second set of data in the storage system. An unavailable state of the first cache is detected. In response to detecting the unavailable state, requests to the first set of data are blocked and at least one space in the second cache is allocated for data in the backup cache. Requests to the first set of data are allowed to proceed after the at least one space is allocated in the second cache and before the data in the backup cache is copied to the at least one allocated space in the second cache. The data from the backup cache is copied to the allocated at least one space in the second cache after the requests to the first set of data are allowed to proceed.

Abstract: Provided is a method, system, and program for destaging data from a first computer readable medium to a second computer readable medium. A list of entries indicating data blocks in the first computer readable medium is scanned. For each entry scanned, a determination is made as to whether the data block indicated in the scanned entry satisfies a criteria. If the data block indicated in the scanned entry satisfies the criteria, then a destage operation is called to destage the data block in the scanned entry from the first computer readable medium to the second computer readable medium. If the called destage operation is not initiated, then the scanned entry is removed from the cache list. The removed scanned entry is added to one destage wait list. During one destage operation, data blocks indicated in entries in the destage wait list are destaged.

Abstract: Provided is a method, system, and program for caching updates to one target storage device in a first and second memories, wherein the target storage device is one of a plurality of storage devices. A determination is made of an allocation of available space in the second memory to the storage devices, wherein a total of the allocation of the available space to all the storage devices exceeds one hundred percent of the available space in the second memory. An update to one target storage device is received and then a determination is made as to whether adding the update to the second memory will exceed the allocation of available space for the target storage device in the second memory. One copy of the update is written to the second memory if adding the update to the second memory will not exceed the allocation of available space for the target storage device.

Abstract: Provided are a method, system, and program for maintaining data in a first cache and second cache, wherein a backup cache maintains a backup copy of data in the first cache, and wherein the first cache is used to cache a first set of data in a storage system and the second cache is used to cache a second set of data in the storage system. An unavailable state of the first cache is detected. In response to detecting the unavailable state, requests to the first set of data are blocked and at least one space in the second cache is allocated for data in the backup cache. Requests to the first set of data are allowed to proceed after the at least one space is allocated in the second cache and before the data in the backup cache is copied to the at least one allocated space in the second cache. The data from the backup cache is copied to the allocated at least one space in the second cache after the requests to the first set of data are allowed to proceed.