Abstract: Apparatus and method for implementing a local proactive hot plug request/acknowledge scheme is disclosed. In a preferred embodiment, each hot pluggable device installable on a computer bus, such as a SCSI bus, is provided with a physical user interface comprising a mechanical request initiator, such as a button or two-position switch, for allowing a user to generate a hot swap request to a controller associated with the bus prior to actual installation of the device on, or removal of the device from, the bus. Upon receipt of the request, the controller determines whether the requested action may be performed, provides a visual indication of its determination to the user via an LED on the user interface and, if installation or removal is determined to be prudent, performs the hot installation/removal in an orderly manner so as not to adversely affect ongoing system operations.

Abstract: A caching disk controller is provided which includes a bus bridge that forms an interface between a memory of the disk controller and a host computer. The caching disk controller further includes a SCSI processor for controlling the transfer of data from a SCSI disk drive to the memory via a local bus. A zero latency DMA controller embodied within the bus bridge snoops the local bus as data is being transferred from the SCSI disk drive to the memory, and thereby allows the data to be sequentially latched within a data FIFO of the bus bridge concurrently with its transfer into the memory. As a result, the requested data may be advantageously provided from the bus bridge to the host computer with reduced delay, while the data continues to be stored within the memory to accommodate high hit rates during subsequent transfers.

Abstract: A disk drive array with a controller which provides: dynamic remapping for grown defects in the disk drives, multi-thread request processing with a variable number of forkings, defect tracking with both logical and physical lists, guarded writes of less than a full stripe optimized by selectably using the redundancy to limit the number of sectors involved, association of multiple operations with a single disk request in order to facilitate error handling, use of an access hiatus as indication of further opportunity to rebuild data in background, and scatter/scatter (bidirectional scatter/gather) operations.

Abstract: A peripheral resource controller such as a caching disk array controller is provided for controlling the transfer of data between a host bus and a peripheral resource, such as an array of hard disk drives. The peripheral resource controller includes a bus interface controller for providing an interface between the host bus and a local bus of the peripheral controller. The bus interface controller further includes a peripheral bus interface which accommodates accesses to a peripheral bus and a DMA controller for controlling direct memory access operations between a local memory of the peripheral controller and a system memory of the host computer. A DMA transfer list memory is coupled to the peripheral bus for storing DMA transfer information. The DMA controller fetches host and local address as well as block size information from the DMA transfer list memory to thereby effectuate DMA operations.

Abstract: A system for reducing the amount of power consumed by a battery operated computer device is disclosed. A microcontroller continuously monitors the activity of at least one I/O device and sets an activity state variable (ASV) associated with the I/O device accordingly. Upon each the expiration of a preselected time period, the microcontroller examines the state of the ASV to determine whether the I/O device was active during the expired time period. If so, the I/O device is caused to operate in a full power mode; otherwise, the I/O device is caused to operate in a reduced power consumption mode. In one embodiment, the I/O device is capable of operating in more than one reduced power consumption mode, in which case, responsive to a determination that the I/O device was not active during the expired time period, the I/O device is caused to operate in the next lowest power consumption mode.

Abstract: A device for interfacing an expansion bus with an option card and an associated method for initializing a computer system having the option card installed on the expansion bus thereof. The interface device includes a dual ported RAM having a first port coupled to the expansion bus and a second port coupled to the option card, a processor coupled to the second port of the dual ported RAM and a non-volatile memory coupled to the processor and to the second port of the dual ported RAM. At power up, the processor transfers an expansion BIOS and pattern stored in the non-volatile memory to first and second portions, respectively, of the memory space of the dual ported RAM. The computer system scans the second portion of the dual ported RAM for the pattern, executes a first initialization sequence contained in the expansion BIOS upon detecting the pattern and then executes a second initialization sequence contained in a BIOS of the computer system.

Abstract: A CD ROM server comprises a CD ROM drive and an array of hard disk drives. Means are provided for copying data from the CD ROM drive to the array of hard disk drives, and for deleting data from the array of hard disk drives, upon receipt of copy and delete requests, respectively, from a host computer system. Means are provided for the host computer to read data from the array of hard disk drives in the CD ROM format that the data had been stored in on the CD ROM. Means are also available to implement RAID technology with the array of hard disk drives for data reconstruction, striping, and redundancy. Means may be provided for the host computer to communicate directly with any SCSI devices connected to the server.

Abstract: Apparatus and method for implementing a local proactive hot plug request/acknowledge scheme is disclosed. In a preferred embodiment, each hot pluggable device installable on a computer bus, such as a SCSI bus, is provided with a physical user interface comprising a mechanical request initiator, such as a button or two-position switch, for allowing a user to generate a hot swap request to a controller associated with the bus prior to actual installation of the device on, or removal of the device from, the bus. Upon receipt of the request, the controller determines whether the requested action may be performed, provides a visual indication of its determination to the user via an LED on the user interface and, if installation or removal is determined to be prudent, performs the hot installation/removal in an orderly manner so as not to adversely affect ongoing system operations.

Abstract: A fault tolerant disk array subsystem is provided that includes a plurality of data drives for storing real data and a parity drive for storing redundant data. Each data drive is associated with a dedicated write-through cache unit and the parity drive is associated with a dedicated write-back cache unit. An array scheduler schedules read and write operations to access the data drives and includes a parity control unit for updating parity information when new data is written to one of the data drives. Since a write-back caching technique is used to store updated parity information, the write latency of the parity drive does not limit the write-throughput of the disk array subsystem. Furthermore, since a non-volatile memory unit is provided to store the addresses of any dirty parity information within the write-back cache unit, parity information can be reconstructed in the event of a power failure.

Abstract: A drive array controller is provided that serves as an interface between both stand-alone SCSI devices as well as SCSI devices that form a composite drive. Since an AHA emulation interface is incorporated on the drive array controller, the drive array controller is compatible with conventional AHA device drivers that drive stand-alone peripheral devices such as SCSI CD-ROM units and SCSI tape drives. The drive array controller includes a SCSI pass-through driver that extracts a SCSI command descriptor block from a command control block created by the AHA device driver. The drive array controller further provides a separate peripheral access channel to support high speed composite drive operations through a composite device driver. Since the AHA emulation interface and a composite drive interface are provided on a common peripheral board, only one EISA expansion slot is occupied.

Abstract: A disk drive array with a controller which provides: dynamic remapping for grown defects in the disk drives, multi-thread request processing with a variable number of forkings, defect tracking with both logical and physical lists, guarded writes of less than a full stripe optimized by selectably using the redundancy to limit the number of sectors involved, association of multiple operations with a single disk request in order to facilitate error handling, use of an access hiatus as indication of further opportunity to rebuild data in background, and scatter/scatter (bidirectional scatter/gather) operations.

Abstract: A method for configuring at least one composite drive for a disk drive array controller. A disk drive array controller having a memory portion on which a list of composite drives which may be installed on a bus of a computer system is stored thereon is provided. A plurality of disk drives are then installed on the bus of the computer system. Each of the disk drives includes a user data region, a first portion of which contains a first field containing a composite drive ID number for a composite drive and a second field which indicates the total number of disk drives in the composite drive corresponding to the composite drive ID number and a second portion of which contains a position of the disk drive within the composite drive corresponding to the composite drive ID number.

Abstract: A disk controller which minimizes the rad operations required during parity writes of less than a single stripe. The disk array can be generalized as including N+1 disk drives with each stripe including a block on each of the N drives storing data and a block in 1 drive storing parity information. The present invention operates during writes to K blocks of a stripe where K is less than N, i.e., a partial stripe write. If K is greater than (N-1)/2, the N-K unwritten blocks are read in order to compute the new parity information before the actual write take place. If K is less than or equal to (N-1)/2, then the controller only reads the old parity information and the old data in the sectors to be written to compute the new parity. Thus the number of reads required to compute the new parity information is minimized.

Abstract: An improved read ahead strategy that improves the performance of a disk array subsystem. The disk controller keeps track of the last n reads to the array. If a new read request is received that is adjacent to any of the last n reads, the controller performs a look ahead read because a sequential read may be in progress. The parameter n is preferably set comparable to or greater than the number of maximum independent activites being performed by the computer system. Therefore, in a multithread system, the controller performs a readahead if any one thread is doing a sequential read.

Abstract: A disk drive array including a controller which provides scatter/scatter (bi-directional scatter/gather) operations between noncontiguous host memory address locations and noncontiguous disk address locations. The host provides a single request to launch a scatter/scatter transfer. The single data request includes a pointer to a list of transfer counts and addresses, the length of the list, and the starting logical address on the disk transfer. Skipped blocks in a scatter/scatter request are specified by data address value of -1, and a no-operation (no-op) request is enqueued for each skipped block. Thus, during reads the controller extends the scattered read from the disk into a single large read of contiguous sectors and suppresses the unwanted data by inserting "no-operation" commands in place of the read commands during the transfer to the host.

Abstract: A disk controller which fragments host requests into atomic requests or one cycle operations prior to execution. The disk controller is coupled to a disk array and receives requests from a host CPU. Host requests are fragmented down to atomic operations. This is highly advantageous for error handling because the controller is not required to determine which phase of an operation is being requested, since every operation is single phase. The present invention includes use of fence markers or execution-control markers to "fence" of mark a block of tasks and ensure that the atomic operations are executed in sequence, if necessary. These markers ensure that related sequences of atomic operations are kept together without, for example, possibly disruptive intervening writes.

Abstract: A disk drive array with a controller which provides: dynamic remapping for grown defects in the disk drives, multi-thread request processing with a variable number of forkings, defect tracking with both logical and physical lists, guarded writes of less than a full stripe optimized by selectably using the redundancy to limit the number of sectors involved, association of multiple operations with a single disk request in order to facilitate error handling, use of an access hiatus as indication of further opportunity to rebuild data in background, and scatter/scatter (bidirectional scatter/gather) operations.