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 dual bus architecture for a computer system including a number of computer system devices and a number of computer system resources. Each of the computer system devices and computer system resources are coupled by first and second communication busses. First and second bus arbitrators provide bus arbitration functions allowing first and second computer system devices to access first and second computer system resources simultaneously. A method of accessing a number of computer system resources by a number of computer system devices coupled by a dual bus architecture is also provided.

Abstract: An apparatus and method for disk mapping and data retrieval includes a data storage medium on which has been stored a plurality of data records. Each record includes at least a record identification portion, for uniquely identifying each record from among the plurality of data records. The apparatus builds a record locator table or high speed semiconductor memory which comprises the unique record identifiers for the records on the storage medium as well as a record locator index generated by the apparatus, which indicates the address of the data record on the storage medium. Data retrieval is facilitated by first searching the record locator table in high speed semiconductor memory for a requested data record. Utilizing the record locator index associated with the requested data record, the system directly accesses the requested data record on the storage medium thereby minimizing storage medium search time.

Abstract: A data storage system which automatically provides and maintains identical secondary data on a preferably geographically remote secondary data storage device. The system includes a primary host computer located in the first geographic location which is coupled to a primary data storage system also located in the first geographic location. The primary data storage system includes at least one primary data storage device on which primary data is to be stored, and a primary data storage system controller which receives data from the primary host computer and controls the storing of the primary data on the primary data storage device.

Abstract: A cache management system and method monitors and controls the contents of cache memory coupled to at least one host and at least one data storage device. A cache indexer maintains a current index of data elements which are stored in cache memory. A sequential data access indicator, responsive to the cache index and to a user selectable sequential data access threshold, determines that a sequential data access is in progress for a given process and provides an indication of the same. The system and method allocate a micro-cache memory to any process performing a sequential data access. In response to the indication of a sequential data access in progress and to a user selectable maximum number of data elements to be prefetched, a data retrieval requestor requests retrieval of up to the selected maximum number of data elements from a data storage device. A user selectable number of sequential data elements determines when previously used micro-cache memory locations will be overwritten.

Abstract: A data storage system with data mirroring and reduced access time data retrieval includes at least one pair of rotating data storage media each having a plurality of generally identical data records. Each rotating data storage medium includes position indicators, for providing one or more indications of the rotational position of each of the rotating data storage media with respect to its associated fixed position read/write mechanism. A position monitor receives the rotational position indications from each rotating data storage medium and computes and monitors the rotational position of each rotating storage medium with respect to its associated read/write mechanism.

Abstract: A cache management system and method monitors and controls the contents of cache memory coupled to at least one host and at least one data storage device. A cache indexer maintains a current index of data elements which are stored in cache memory. A sequential data access indicator, responsive to the cache index and to a user selectable sequential data access threshold, determines that a sequential data access is in progress for a given process and provides an indication of the same. The system and method allocate a micro-cache memory to any process performing a sequential data access. In response to the indication of a sequential data access in progress and to a user selectable maximum number of data elements to be prefetched, a data retrieval requestor requests retrieval of up to the selected maximum number of data elements from a data storage device. A user selectable number of sequential data elements determines when previously used micro-cache memory locations will be overwritten.

Abstract: A disk storage system including means for assuring completion of data writes to a data storage disk upon failure of electrical power receives data write commands including data to be written to one or more storage disks. Temporary memory storage temporarily stores the write commands including data to be written to one or more storage disks. The system generates a disk write pending indicator associated with each datum to be written to the one or more storage disks, for indicating that the data stored in the temporary memory must be written to disk. A disk director searches the temporary memory storage for data stored in the temporary memory storage that must be written to disk as indicated by the associated data write pending indicator, for writing the data to the one or more storage disks.

Abstract: A reconfigurable, multi-function data controller for use in a data storage system is selectively adaptable for use as a data channel adapter or a storage device adapter. The controller includes a data channel interface having at least one independent, bi-directional channel interface, for transmitting and receiving commands, data and status with one or more host computers. At least one memory interface transmits and receives commands and data to and from at least one high speed semiconductor memory unit. Additionally, a data storage interface controls and transmits data to and from one or more data storage devices such as a disk drive. A multi-function controller director is coupled to the data channel interface, the at least one memory interface, and the data storage device interface, for directing the reconfigurable multi-function data controller to function as either a data channel adapter or as a storage device adapter in response to selected commands received by the director.

Abstract: A dynamically reconfigurable data storage system includes a plurality of storage system controllers, each of which is selectively operable at any given time as one of a channel adapter and a storage device adapter as established by commands received by each of the controllers. At least one semiconductor memory is coupled to the storage system controllers. Additionally, a data storage system director issues commands to each of the storage system controllers for establishing a first quantity of the system controllers as channel adapters, for transmitting and receiving at least data and commands to and from one or more host computers over a plurality of data communication channels. The data storage system director also establishes a second quantity of the storage system controllers as storage device adapters, for cotrolling data transfer to and from a plurality of data storage devices.

Abstract: An apparatus and method for disk mapping and data retrieval includes a data storage medium on which has been stored a plurality of data records. Each record includes at least a record identification portion, for uniquely identifying each record from among the plurality of data records. The apparatus builds a record locator table and high speed semiconductor memory which comprises the unique record identifiers for the records on the storage medium as well as a record locator index generated by the apparatus, which indicates the address of the data record on the storage medium. Data retrieval is facilitated by first searching the record locator table in high speed semiconductor memory for a requested data record. Utilizing the record locator index associated with the reqested data record, the system directly accesses the requested data record on the storage medium thereby minimizing storage medium search time.

Abstract: A system for generating memory timing signals and for reducing memory access time includes a plurality of memory modules having an array of memory cells addressable in response to a number of row address select and column address select signals. A row address select signal generator associated with each memory module generates row address signals upon the system receiving a request for access to any memory storage location. At least one memory array selection comparator compares memory address signals with preselected, unique, memory module addresses, for identifying a selected memory module, and for providing a column address signal generator enable signal to the column address select signal generator of the selected memory module.