System and method for command queuing on raid levels 4 and 5 par

Details System and method for command queuing on raid levels 4 and 5 par System and method for command queuing on raid levels 4 and 5 par

1993-12-30

1996-06-25

Beausoliel, Jr., Robert W.

Excavating

371 511, 395441, G06F 1134

Patent

active

055309488

ABSTRACT:
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.

REFERENCES:
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patent: 5191584 (1993-03-01), Anderson
patent: 5195100 (1993-03-01), Katz et al.
patent: 5208813 (1993-05-01), Stallmo
patent: 5263145 (1993-11-01), Brady et al.
patent: 5309451 (1994-05-01), Noya et al.
patent: 5341381 (1994-08-01), Fuller
patent: 5353424 (1994-10-01), Partoui et al.
patent: 5373512 (1994-12-01), Brady

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