Other

International Business Machines Corporation

S M Islam

Bruce M Cassidy

An apparatus for providing identification information to a peripheral device connected to a data processing system via a parallel communications interface cable. The apparatus includes a cable connector for connecting to a cable coupled to the data processing system and a peripheral device connector for connecting to the peripheral device. The cable connector and the peripheral device connector are coupled together to provide communication between the data processing system and the peripheral device. The apparatus also includes means for providing identification information to the connected peripheral device. Such identification information is utilized by the peripheral device to set a device identifier. In one embodiment, device identifiers are set utilizing identification information selected in conjunction with the physical location of the peripheral device. In one embodiment, the apparatus is utilized to connect a SCSI hard disk drive to a data processing system and to provide the SCSI hard disk drive information necessary to set a SCSI device identification number.

Method and apparatus for automatically assigning device identifiers on a

The queuing of commands on an input/output controller for a parity drive, in a level 4 or level 5 redundant array of inexpensive disk drives responds to receipt of a write instruction with appended data by determining a logical block address of a data drive for the appended data and a logical block address of a parity drive for redundant data belonging to a destination stripe of the appended data. If a parity cache entry corresponds to the parity address, a cache hit has occurred. Responsive to a cache hit, computation of replacement parity data for the stripe may be done from parity data in cache at a location given by the parity cache entry, data read from the data drive and the appended data. The newly calculated parity data is then placed in cache. A command is then sent to an input/output controller for the drive where the parity data is located to write the replacement parity data. Serialization of access to the parity data is moved from the disk drive to cache memory, allowing command queuing to be used with the disk drive to preserve optimum available performance of the drive.

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Boca Raton, FL, United States of America

S M Islam