Abstract: Guaranteeing space availability for thin devices includes reserving space without committing, or fully pre-allocating, the space to specific thin device ranges. Space may be held in reserve for a particular set of thin devices and consumed as needed by those thin devices. The system guards user-critical devices from running out of space, for example due to a “rogue device” scenario in which one device allocates an excessive amount of space. The system uses a reservation entity, to which a thin device may subscribe, which reserves space for the thin device without allocating that space before it is need to service an I/O request.

Abstract: Described are techniques for performing data storage management. A first data portion is stored at a first logical address of a first device that is mapped to a first physical storage location at which the first data portion is stored. A second data portion is stored at a second logical address on a second device that is mapped to a second physical storage location at which the second data portion is stored. The first data portion is a duplicate of data contents of the second data portion and the first physical storage location is the same physical storage location as the second physical storage location. The first device and the second device are thin devices where physical storage is unallocated for at least a portion of each thin device's storage capacity at a point in time.

Abstract: Automatically allocating storage space for a storage pool includes providing at least one spares pool containing unused data devices and moving at least one the unused data devices to the storage pool in response to a write causing the available space of the storage pool to be exceeded and/or the available storage space of the storage pool exceeding a predetermined amount. The predetermined amount may be an amount of used storage space that varies according to at least one of: the size and activity level of the pool. The data devices may be logical devices. The pools may correspond to storage space in a single storage device or may correspond to storage space in multiple storage devices.

Abstract: Handling a write operation to write data to a section of a storage device includes determining if the section needs to be copied to at least a first target device and, if the section of the storage device needs to be copied to the at least first target device, providing the data to a memory location and confirming completion of the write operation prior to copying the section of the storage device to the at least first target device. Handling a write operation to write data to a section of a storage device may also include determining if a slot in a cache memory corresponding to the section of the storage device needs to be copied to at least a second target device. If so, then in some cases the slot may be copied to the at least second target device prior to providing the data to the memory location.

Abstract: A PRECOPY command identifies source and destination devices. Data begins to transfer from the source device to the destination device in a background mode under the control of a copy program that transfers the data on a track-by-track basis. Changes to the data tracks are monitored in three lists. The copy program monitors the first two lists to determine when a data track in a source device has been written and needs to be retransferred to the destination device to provide the most up to date data. Procedures assure that any data access to a particular track in either the source by any application prior to the activation of a formal transfer are accommodated to maintain data integrity. An ACTIVATE command makes the destination device available to another application and activates another copy operation. Procedures assure that any data access to a particular track in either of the source or destination devices by any application prior to the transfer of that track are accommodated to maintain data integrity.