Provided are a computer program product, system, and method for prefetching cache resources for a write request from a host to tracks in storage cached in a cache. Cache resources held for a plurality of tracks in a write set are released before expected writes are received for the tracks in the write set. Cache resources for tracks in the write set are obtained, following the release of the cache resources, to use for expected write requests to the tracks in the write set.

A daisy-chain storage synchronization (DSS) system and method that permits a daisy-chain of interconnected pass-thru disk drive controllers (PTDDCs) each connected to a SATA local disk drive (LDD) disk storage element (DSE) to support state synchronization within PTDDCs in the daisy-chain is disclosed. The PTDDCs within the daisy-chain are configured to individually maintain drive state information (DSI) relating to the LDD as well as chain state information (CSI) relating to the individual PTDDCs within the daisy-chain. This state information may be modified on receipt of out-of-band signaling (OBS) from other PTDDC elements up the daisy-chain as well as OBS from other PTDDC elements down the daisy-chain, CSI is determined in part by conventional SATA OBS state register protocols that are modified by internal state registers (ISR) in each individual PTDDC daisy-chain element so as to make the DSS transparent to existing SATA OBS single-disk standard hardware command protocols.

Methods, devices and systems are provided for making a shingled magnetic recording (SMR) hard disk drive operate with similar random access characteristics of a conventional hard drive despite the SMR disk having strict sequential write requirements. A virtual space manager manages a virtual address space, which is visible to a host system, and maps virtual addresses to logical addresses on the SMR disk. A logical space manager controls the placement of data on the SMR disk and ensures that writes to the disk comply with the sequential write requirements. The disk is subdivided into a plurality of stripes each comprising one or more blocks. When a block located within a stripe is to be rewritten with new data, the entire stripe is read from the SMR disk into a memory of the system, the stripe is modified in the memory to replace the previous data stored in the block with the new data, and the modified stripe is written to a new, next available stripe on the disk.

A technique for adapting over-provisioning space in a storage system includes determining one or more workload characteristics in the storage system. Over-provisioning space in the storage system is then adjusted to achieve a target write amplification for the storage system, based on the workload characteristics.

A technique for garbage collection in a storage system includes generating regrouping metadata for one or more pages of at least two logical erase blocks (LEB). The regrouping metadata indicates an associated stream for each of the pages. Multiple of the LEBs that include valid pages associated with a first stream are selected, based on the regrouping metadata, for regrouping. The valid pages associated with the first stream from the selected LEBs are regrouped into a new LEB.

Provided are a computer program product, system, and method for providing track access reasons for track accesses resulting in the release of prefetched cache resources for the track. A first request for a track is received from a process for which prefetched cache resources to a cache are held for a second request for the track that is expected. A track access reason is provided for the first request specifying a reason for the first request. The prefetched cache resources are released before the second request to the track is received. Indication is made in an unexpected released track list of the track and the track access reason for the first request.

Systems and methods presented herein provide for region lock management in an expander. In one embodiment, an expander, being operable to link a plurality of initiators to a plurality of Redundant Array of Independent Disks logical volumes, includes a plurality of physical transceivers, each being operable to link the logical volumes to the initiators, and a region lock manager operable to receive a request from a first of the initiators to lock a region of the logical volumes for an input/output operation by the first initiator. The region lock manager is also operable to determine if the requested region is unlocked, to lock the requested region from the remaining initiators to allow the input/output operation of the first initiator after determining the requested region is unlocked, and to unlock the requested region after the input/output operation of the first initiator is complete.

In accordance with a method of the invention, host data, accompanied by host LBA, is received from a host. If the host data is determined not to be a duplicate host data, an available intermediate LBA (iLBA) is identified and the host LBA is linked to the identified iLBA. During writing of the received host data to the SSDs, an available SLBA is identified and saved to a table at a location indexed by the identified iLBA. Accordingly, the next time the same host data is received, it is recognized as a duplicate host data and the host address accompanying it is linked to the same iLBA, which is already associated with the same SLBA. Upon this recognition, an actual write to the SSDs is avoided.

A system and method for improving storage system operation is disclosed. A storage system includes a first tier with high-performance redundancy and a second tier with capacity efficient redundancy. The first tier and the second tier are built from the same storage devices in a storage pool so each storage device includes both the first and second tiers. The storage system stores write data initially to the first tier. When demand for the data falls below a threshold, the storage system migrates the write data to the second tier. This is done by changing the mapping of underlying physical locations on the storage devices where the write data is stored so that the underlying physical locations are logically associated with the second tier instead of the first tier. After remapping, the storage system also computes parity information for the migrated write data and stores it in the second tier.

A cache storage method includes providing a storage cache cluster, comprising a plurality of cache storage elements, for caching I/O operations from a plurality of virtual machines associated with a corresponding plurality of virtual hard disks mapped to a logical storage area network volume or LUN. Responsive to a cache flush signal, flush write back operations are performed to flush modified cache blocks to achieve or preserve coherency. The flush write back operations may include accessing current time data indicative of a current time, determining a current time window in accordance with the current time, determining a duration of the current time window, and identifying a current cache storage element corresponding to the current time window. For a duration of the current time window, only those write back blocks stored in the current cache storage element are flushed. In addition, the applicable write back blocks are flushed in accordance with logical block address information associated with each write back block.