Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Patent
1997-11-04
2000-11-07
Cabeca, John W.
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
711151, 710 6, 710 43, 710 45, G06F 1200
Patent
active
061450529
ABSTRACT:
A method for selecting a next command to execute from a set of SCSI commands where the commands are gracefully aged and performance of a disk drive is improved. An execution threshold age, a pool threshold age, and an age threshold age are used to determine what command is executed next. A mechanical time delay is calculated for a command based on the time required to position the read/write head over the data location requested in each command. A command age is calculated based on a current time and the time the command was received from the host. The command age is checked against the execution threshold age and pool threshold age. Any commands that have aged beyond the execution threshold age are executed. If the oldest command has aged beyond the age threshold age, then any command that has both aged beyond the pool threshold age and has the smallest mechanical time delay is executed, otherwise the command with the smallest mechanical time delay is executed. Alternatively, a time stamp of the oldest command is compared against an age threshold to determine if all or some of the commands are in the pool of commands. If there are no commands that have aged beyond the age threshold, then the command that has the smallest mechanical time delay is executed first.
REFERENCES:
patent: 5729718 (1998-03-01), Au
patent: 5765204 (1998-06-01), Bakke et al.
patent: 5787482 (1998-07-01), Chen et al.
Howe Steven M.
Williams Jeffrey L.
Anderson Matthew D.
Cabeca John W.
Shara Milad G.
Western Digital Corporation
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