Abstract: An apparatus and method is disclosed which enables a host computer to adjust the caching strategy used for writing its write request data to storage media during execution of various software applications. The method includes the step of generating a caching-flushing parameter in the host computer. The cache flushing parameter is then transferred from the host computer to a controller which has a cache memory. Thereafter, a quantity of write request data is written from the cache memory to a storage medium in accordance with the cache-flushing parameter.

Abstract: A method and apparatus for increasing performance in a data processing system. The data processing system includes a plurality of storage devices and a backup storage device. The backup storage device is configured as a log device. Data is logged to the backup storage device after the backup storage device has been configured as a log device. In response to a failure of a storage device within the plurality of storage devices, the backup storage device is reconfigured to be used as a replacement for the failed storage device.

Abstract: The invention relates to a method and apparatus for maintaining data/parity consistency in a RAID data storage system. The invention utilizes reserved disk storage space in the RAID array to log data necessary to restore data/parity consistency should an interruption event, such as a power failure, corrupt the data stored in a particular redundancy group. In one embodiment, the invention logs new data and new parity information to the reserved disk storage space before the new data and new parity information are written to the appropriate locations in the associated redundancy group. In this way, if an interruption event occurs when either the new data or the new parity information has already been written to the redundancy group but the other has not, the corresponding data and parity information stored in the reserved disk storage space can be used to restore data/parity consistency after the event has ended.

Abstract: The invention provides a method and apparatus for increasing the efficiency of data transfer between a host computer and a disk array in a RAID system. The invention operates by splitting up large I/O requests from the computer into smaller, more manageable pieces and processing the pieces as though they were individual I/O requests. In one embodiment, the invention keeps only a limited number of these smaller individual I/O requests "active" at any particular time so that a single large I/O request cannot preclude other I/O requests from making progress in the controller. Both the size of the smaller I/O request pieces and the limited number of these pieces which will be "active" at any one time may be tunable parameters. The invention improves the efficiency of data transfer between the host computer and the array of disk drives by providing for increased overlap of activity in the controller. This increased overlap of activity results in increased controller throughput.

Abstract: Methods and associated apparatus operable in a RAID subsystem to improve the speed and flexibility of initializing the subsystem by storing configuration and identification information in a reserved area on each disk drive in the subsystem. The reserved area on each disk drive of the disk array contains a unique identifier to identify the particular disk drive from all others and further contains group configuration information regarding all groups in which the particular disk drive is a member. The configuration and identification information is generated and written to each disk drive in the disk array when the particular disk drive is configured so as to be added or deleted from groups of the subsystem. Upon subsystem reset (e.g. power on reset or other reset operations), the RAID controller in the subsystem determines the proper configuration of the RAID groups despite temporary unavailability or physical relocation of one or more disk drives in the disk array.

Abstract: Methods and associated data structures operable in a RAID subsystem to improve I/O performance. A two level cache data structure and associated methods are implemented with a RAID controller. The lower level cache comprises buffers holding recently utilized blocks of the disk devices. The upper level cache records which blocks are present in the lower level cache for each stripe in the RAID level 5 configuration. The upper level cache serves to reduce the overhead processing required of the RAID controller to determine which blocks are present in the lower level cache. Having more rapid access to this information by lowering the processing overhead enables the present invention to rapidly select between different write techniques to post data and error blocks from low level cache to the disk array. A RMW write technique is used to post data and error checking blocks to disk when insufficient information reside in the lower level cache.

Abstract: A high performance scaleable hardware architecture for a disk array storage subsystem which supports RAID modes 0, 3, 4 and 5. The architecture features a high bandwidth parity calculation engine, a buffered PCI interface operating at the full speed of the PCI bus, and a dedicated local memory. The dedicated local memory is dual ported so that PCI and parity operations may operate concurrently. The architecture of the disk array controller allows parity calculations and memory block moves to occur without interfering with the controller processor or its associated memory, freeing the controller processor to manage array task control. The array controller configuration allows simultaneous operation of data block moves between storage I/O devices and local memory; data block moves between host SCSI connections and local memory; parity calculations; and normal CPU memory fetches, queued operations for block moves and queued operations for parity tasks.