International Business Machines Corporation

Hitachi Global Storage Technologies Netherlands B.v.

Brian Lee Morger

Shad Henry Thorstenson

Louise Ann Marier

Jeffrey Richards Hester

Christopher David Wiederholt

Richard Rolls

Peter Allen Cummings

Michael James Miller

Teras Eve Yonker

A SCSI ID of a SCSI initiator device that has won an arbitration is identified on a SCSI bus and stored in a register at a SCSI device. Subsequently, a SCSI ID of a selected SCSI target device which was selected by the SCSI initiator device is identified on the SCSI bus and compared with the SCSI ID in the register. If the SCSI ID of the selected SCSI target device and the SCSI ID stored in the register are different, a SCSI command from the SCSI initiator device is processed by the selected SCSI target device. If the SCSI ID of the selected SCSI target device and the SCSI ID stored in the register are the same, the selected SCSI target device refrains from processing the SCSI command from the SCSI initiator device.

Methods and apparatus for improving data integrity for small computer system interface (SCSI) devices

A peripheral device (which is preferably a disk drive) can automatically collect trace data upon detecting certain error conditions. The peripheral device has the ability to selectively alter the range of state data collected in a trace depending on the error type. Preferably, the device includes a programmable processor executing a control program. A set of trace switches, each enabling a corresponding set of trace points, can be independently set by the control program. An error trace identification table identifies, for each error type, a corresponding set of trace switches. If an error is encountered, the trace switches corresponding to the error type are determined from the table, and the switches are set accordingly. In another invention aspect, a set of trap switches in the device can be set to trap on the occurrence of a specific error type, thereby supporting a more detailed error analysis.

Method and apparatus for obtaining diagnostic data for a device attached to a computer system

A data storage device and method for improving the performance of data storage devices examines a command queue and performs data transfers to memory within the device before prior commands have completed. A process running in the idle loop of the controller in the storage device checks the queue for write requests and if a cache space within a dual-port cache to hold the transfer data is available, the data transfer portion of the transfer is completed, while the device is still waiting for completion of prior commands in the queue, and data transfers are completing from the cache to the physical media for the prior command.

Data storage device and method for reducing write misses by completing transfer to a dual-port cache before initiating a disk write of the data from the cache

In a method of and a system for managing reselection of an initiator by a target on a SCSI bus, the target attempts to secure control of the bus for a first reselection cycle to reselect the initiator. If the target fails to secure control of the bus for the first reselection cycle and the target is selected by the initiator for a selection cycle, the target processes the selection cycle. However, concurrently with processing the selection cycle, substantially immediately after the bus becomes free, and before the target completes processing the selection cycle, the target attempts to secure control of the bus for a second reselection cycle to reselect the initiator.

Method of and system for managing reselection on a SCSI bus

A method and apparatus are provided for controlling communications on a small computer system interface (SCSI). A cache memory is arranged for storing an input queue, a status queue and a cache operation queue. An input engine detects unsolicited data from the SCSI and transfers the detected unsolicited data to the input queue. A status engine transfers status information between the SCSI and the status queue. A cache engine transfers data between the SCSI and the cache operation queue. Each of the input engine, the status engine, and the cache engine is independent to enable full duplex operation. A connection arbitrator is shared between the input engine, the status engine, and the cache engine enabling a connection to be shared by the input engine, the status engine, and the cache engine.

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Preston, MN, United States of America

Brian Lee Morger