Abstract: A shared system memory, such as a cache, buffers Input/Output (I/O) requests between one or more host computers and one or more data storage servers or devices. The cache may be configured to operate natively as a least-recently-used (LRU)-only cache and may be optimized for random data accesses. Data buffered by the cache may be part of a sequential data stream for which prefetching data is desirable. A remote prefetch module is provided between the cache and the host to conduct prefetching without internally modifying the cache. The remote prefetch module maintains a model of the cache. Using the model, the prefetch module anticipates whether data is likely to be part of a sequential steam of data passed between a host and a data storage device. If so, the prefetch module schedules a prefetch of the data. The prefetch may be achieved by sending an I/O request to the data server or device.

Abstract: In a storage system comprising an array of storage devices, including a processor and memory, a plurality of logical tracks are organized on the storage devices in segments comprising columns striped across the storage devices. A system and method are provided for storing logical tracks in the storage devices. Sequentially logically related logical tracks are stored together in neighborhoods. Logical tracks of the same neighborhood destaged at the same time are assigned to a single open segment with other logical tracks of the same neighborhood type. The time at which open segments are designated as closed segments to be written to the storage devices is based on performance, disk utilization and memory utilization criteria. Logical tracks are never split between segment columns. Also, attempts are made not to split a neighborhood of logical tracks being destaged together between segment columns.

Abstract: In a storage system comprising an array of storage devices, including a processor and memory, a plurality of logical tracks are organized on the storage devices in segments comprising columns striped across the storage devices. A system and method are provided for storing logical tracks in the storage devices. Sequentially logically related logical tracks are stored together in neighborhoods. Logical tracks of the same neighborhood destaged at the same time are assigned to a single open segment with other logical tracks of the same neighborhood type. The time at which open segments are designated as closed segments to be written to the storage devices is based on performance, disk utilization and memory utilization criteria. Logical tracks are never split between segment columns. Also, attempts are made not to split a neighborhood of logical tracks being destaged together between segment columns.

Abstract: In a storage system comprising an array of storage devices, including a processor and memory, a plurality of logical tracks are organized on the storage devices in segments comprising columns striped across the storage devices. A system and method are provided for storing logical tracks in the storage devices. Sequentially logically related logical tracks are stored together in neighborhoods. Logical tracks of the same neighborhood A0 destaged at the same time are assigned to a single open segment with other logical tracks of the same neighborhood type. The time at which open segments are designated as closed segments to be written to the storage devices is based on performance, disk utilization and memory utilization criteria. Logical tracks are never split between segment columns. Also, attempts are made not to split a neighborhood of logical tracks being destaged together between segment columns.

Abstract: A data processing system dynamically balances allocation of storage areas in a shared coupling facility that is devoted to storage of directory entries and data blocks. Each directory entry includes information regarding the validity of a data block that is locally stored by one or more processor modules in the data processing system. The system includes a coupling facility having a cache memory wherein a first portion is allocated to storage of data blocks and a second portion is allocated to storage of directory entries. Each directory entry, associated with a data block, indicates the validity or invalidity of data contained in a copy of the data block maintained by a connected computer module in its local memory. Each computer module, upon requiring a first data block and determining that (i) the first data block is present in its local memory (i.e., a buffer "hit"), but (ii) is not marked valid and (iii) is not present in the coupling facility (i.e.

Abstract: A system and method are provided for managing persistent and non-persistent data in a log structured disk array. In a log structured array, data are first collected in a log stored in a buffer. When the buffer is full, the data are written to a disk drive. Persistent data are continually accessed over a long period of time such that, most disk activity is associated with persistent data. Preferably, the persistent data are stored in the part of the disk where access times are minimal (active region), such as in the middle cylinders of a disk. When writing data (including during garbage collection procedure) persistent data is written to the active region and non-persistent data is written to the other regions (inactive region). The persistence of the data is monitored. Persistent data is migrated to the active region and non-persistent is migrated to the inactive region.

Abstract: Methods and systems are disclosed which utilize Little's law to improve cache management in a computer based storage system in which the cache is a partitioned or non partitioned write-back cache. In a first aspect, a method and system for managing a write-back cache in a computer based system to accommodate for deferred write operations is disclosed. The method .and system comprises determining an average cast out delay for a cache entry. In a second aspect the method and system comprises utilizing the average castout delay for estimating the number of dirty cache entries which will be needed by the cache if the write operations rate and the average cast out delay does not change significantly. In a third aspect, a method and system for managing a partitioned and prioritized cache in a computer based system to provide sensitivity to a local maximum is disclosed.