Abstract: A data network with data storage facilities for providing redundant data storage and for enabling concurrent access to the data for multiple purposes. A first data processing system with a first data facility stores a data base and processes transactions or other priority applications. A second data storage facility, that may be physically separated from the first data storage facility, mirrors the data in the first data storage facility. In a concurrent access operating mode, the second data storage facility makes the data available to an application concurrently with, but independently of, the operation of the other application. On completion of the concurrent operation, the second data storage facility can reconnect with and synchronizes with the first data storage facility thereby to reestablish the mirroring operation.

Abstract: A method and apparatus for assuring data consistency in a data processing network including local and remote data storage controllers interconnected by independent communication paths. The remote storage controller or controllers normally act as a mirror for the local storage controller or controllers. If, for any reason, transfers over one of the independent communication paths is interrupted, transfers over all the independent communication paths to predefined devices in a group are suspended thereby assuring the consistency of the data at the remote storage controller or controllers. When the cause of the interruption has been corrected, the local storage controllers are able to transfer data modified since the suspension occurred to their corresponding remote storage controllers thereby to reestablish synchronism and consistency for the entire dataset.

Abstract: A system and method for providing on-line, real-time, transparent data migration from an existing storage device to a replacement storage device. The existing and replacement storage devices are connected as a composite storage device that is coupled to a host, network or other data processing system. The replacement storage device includes a table which identifies data elements that have migrated to the replacement storage device. When a host system makes a data transfer request for one or more data elements, the replacement storage device determines whether the data elements have been migrated. If the data elements have migrated, the replacement storage device responds to the data transfer request independently of any interaction with the existing storage device. If the data elements have not migrated, the replacement storage device migrates the requested data elements and then responds to the data request and updates the data element map or table.

Abstract: A data processing network including a local system and a geographically remote system. Each of the local and remote systems includes a data storage facility. The remote data storage facility mirrors the local data storage facility. In a normal operating mode, the local and remote systems operate in near synchronism or in synchronism. In an alternate operating mode, writing operations at the local system immediately update the storage devices in the local data storage facility. Transfers of corresponding data to the remote data storage facility are made independently of and asynchronously with respect to the operation of the local system.

Abstract: Load balancing of activities on physical disk storage devices is accomplished by monitoring reading and writing operations to blocks of contiguous storage locations on the physical disk storage devices. A list of exchangeable pairs of blocks is developed based on size and function. Statistics accumulated over an interval are then used to obtain access activity values for each block and each physical disk drive. These activities are represented as disk seek, latency and data transfer times. A statistical analysis leads to a selection of one block pair. After testing to determine any adverse effect of making that change, the exchange is made to more evenly distribute the loading on individual physical disk storage devices.

Abstract: A data storage facility that allows data on a standard device to be replicated to other storage devices for independent and concurrent access. The standard device includes first and second tables for monitoring the operation of the standard device. The other storage device that receive the copies have tables that identify their status. The system utilizes these tables in various combinations to enable multiple copies to be altered and updated.

Abstract: A mechanism for optimizing predictive read performance in a data storage system that is connected to a geographically remote data storage system by a data link for remote replication of data in support of data recovery operations. The data storage system initiates a local prefetch and initiates via the data link a remote prefetch by the remote data storage system to retrieve data from storage devices coupled to the local and remote data storage systems, respectively. The remote prefetch read start address is offset from the local prefetch read start address by a programmable track offset value. The programmable track offset value is adjusted to tune the prefetch workload balance between the local and remote data storage systems.

Abstract: A data network with a remote data facility for providing redundant data storage and for enabling concurrent point-in-time backup operations. A local data processing system with a data facility stores a data base and processes applications. A second system, physically separated from the first system, includes a data facility that normally mirrors the data in the first system. In a backup mode, the second system is enabled to transfer data from its data facility to a backup facility concurrently with, but independently of, the operation of the first system. On completion of the backup operation, the second system reconnects with and synchronizes with the first system thereby to reestablish the mirroring operation of the second system.

Abstract: A data network with data storage facilities for providing redundant data storage and for enabling concurrent access to the data for multiple purposes. A first data processing system with a first data facility stores a data base and processes transactions or other priority applications. A second data storage facility, that may be physically separated from the first data storage facility, mirrors the data in the first data storage facility. In a concurrent access operating mode, the second data storage facility makes the data available to an application concurrently with, but independently of, the operation of the other application. On completion of the concurrent operation, the second data storage facility can reconnect with and synchronizes with the first data storage facility thereby to reestablish the mirroring operation.

Abstract: A method and apparatus for assuring data consistency in a data processing network including local and remote data storage controllers interconnected by independent communication paths. The remote storage controller or controllers normally act as a mirror for the local storage controller or controllers. If, for any reason, transfers over one of the independent communication paths is interrupted, transfers over all the independent communication paths to predefined devices in a group are suspended thereby assuring the consistency of the data at the remote storage controller or controllers. When the cause of the interruption has been corrected, the local storage controllers are able to transfer data modified since the suspension occurred to their corresponding remote storage controllers thereby to reestablish synchronism and consistency for the entire dataset.

Abstract: A method and apparatus for enabling a common data set to be utilized by multiple data processes. During a first operating mode, first and second data stores in a data storage facility with a common buffer attach to a first data process and act as mirrors. Data to be written transfers to the common buffer and then to the data stores. A second command produces a split whereby the first data store remains attached to the first data process and the second data store is available to the second data process. After the second command is executed, any data in the common buffer is transferred to the corresponding data stores in parallel with and transparently to the actions between the first and second data processes and the first and second data stores, respectively.

Abstract: Method and apparatus are disclosed for copying and backing up logical objects in a computer storage system. The logical objects are comprised of data blocks. The data blocks may be copied in any order. The data blocks may be copied or written from a storage media, such as a tape, in parallel.

Abstract: Load balancing of activities on physical disk storage devices is accomplished by monitoring reading and writing operations to blocks of contiguous storage locations on the physical disk storage devices. A list of exchangeable pairs of blocks is developed based on size and function. Statistics accumulated over an interval are then used to obtain access activity values for each block and each physical disk drive. These activities are represented as disk seek, latency and data transfer times. A statistical analysis leads to a selection of one block pair. After testing to determine any adverse effect of making that change, the exchange is made to more evenly distribute the loading on individual physical disk storage devices.

Abstract: Two data storage systems are interconnected by a data link for remote mirroring of data. Each volume of data is configured as local, primary in a remotely mirrored volume pair, or secondary in a remotely mirrored volume pair. Normally, a host computer directly accesses either a local or a primary volume, and data written to a primary volume is automatically sent over the link to a corresponding secondary volume. Each remotely mirrored volume pair can operate in a selected synchronization mode including synchronous, semi-synchronous, adaptive copy-remote write pending, and adaptive copy-disk. Direct write access to a secondary volume is denied if a “sync required” attribute is set for the volume and the volume is not synchronized. If a “volume domino” mode is enabled for a remotely mirrored volume pair, access to a volume of the pair is denied when the other volume is inaccessible.

Abstract: A data processing network including a local system and a geographically remote system. Each of the local and remote systems includes a data storage facility. The remote data storage facility mirrors the local data storage facility. In a normal operating mode, the local and remote systems operate in near synchronism or in synchronism. In an alternate operating mode, writing operations at the local system immediately update the storage devices in the local data storage facility. Transfers of corresponding data to the remote data storage facility are made independently of and asynchronously with respect to the operation of the local system.

Abstract: In one embodiment, mirroring communication from a second source storage device to a second target storage device in a data mirroring system is disabled when mirroring communication from a first source storage device to a first target storage device is disabled. In another embodiment, information is stored in a data mirroring system identifying at least one subset of a plurality of mirrored source storage devices for which a consistent representation of data is desired to be maintained on at least one corresponding subset of a plurality of target storage devices. In yet another embodiment, at least one of a plurality of mirrored source storage devices is placed in one of a first state, a second state, and a third state. In response to a source storage system receiving a write-requesting command chain directed to a mirrored source storage device in the first state, the command chain is permitted to commit and data written by the command chain is transferred to a corresponding target storage device.

Abstract: A system and method for dynamically modifying parameters in a data storage system such as a RAID system. Such parameters include QOS (Quality of Service) parameters, which control the speed in which system operations are performed for various parts of a data storage system. The storage devices addressable as logical volumes can be individually controlled and configured for preferred levels of performance and service. The parameters can be changed at any time while the data storage system is in use, with the changes taking effect very quickly. These parameter changes are permanently stored and therefore allow system configurations to be maintained. A user interface (UI) allows a user or system administrator to easily observe and configure system parameters, preferably using a graphic user interface which allows a user to select system changes along a scale from minimum to a maximum.

Abstract: Method and apparatus for copying, transferring, backing up and restoring data are disclosed. The data can be copied, backed up or restored in segments sizes larger than the data blocks which comprise a logical object. In some embodiments, the segment can correspond to a track of a primary storage device and the data blocks to a fixed size block. In some instances, copying, storage and transfer of the segments which include multiple data blocks can result in transfer of a data block not in a logical object.

Abstract: A data processing network including a local system and a geographically remote system. Each of the local and remote systems includes a data storage facility. The remote data storage facility mirrors the local data storage facility. In a normal operating mode, the local and remote systems operate in near synchronism or in synchronism. In an alternate operating mode, writing operations at the local system immediately update the storage devices in the local data storage facility. Transfers of corresponding data to the remote data storage facility are made independently of and asynchronously with respect to the operation of the local system.

Abstract: Storing data in a cache memory includes providing a first mechanism for allowing exclusive access to a first portion of the cache memory and providing a second mechanism for allowing exclusive access to a second portion of the cache memory, where exclusive access to the first portion is independent of exclusive access to the second portion. The first and second mechanisms may be software locks. Allowing exclusive access may also include providing a first data structure in the first portion of the cache memory and providing a second data structure in the second portion of the cache memory, where accessing the first portion includes accessing the first data structure and accessing the second portion includes accessing the second data structure. The data structures may doubly linked ring lists of blocks of data and the blocks may correspond to a track on a disk drive. The technique described herein may be generalized to any number of portions.