Method and apparatus for selecting enqueued data access...

Details Method and apparatus for selecting enqueued data access... Method and apparatus for selecting enqueued data access...

2006-01-31

2006-01-31

Padmanabhan, Mano (Department: 2188)

Electrical computers and digital processing systems: memory

Storage accessing and control

Specific memory composition

C711S111000

Reexamination Certificate

active

06993624

ABSTRACT:
In accordance with one aspect of the present invention, a seek profile table used by a disk controller contains multiple profiles for seek operations, and is accessed by a separate index table containing, for each permutation of key parameters, an index to a corresponding profile. In operation, the estimated seek time for an enqueued data access operation is obtained by accessing the applicable index table entry, using the value of the index entry to determine the corresponding profile, and using the profile to estimate the access time. Preferably, a “time-based relocation expected access time” algorithm is used, in which a nominal seek time is established, and profile table entries express a probability that an operation with a given latency above the nominal seek time will complete within the latency period. The expected access time is the latency plus the product of this probability and the time cost of a miss, i.e., the time of a single disk revolution.

REFERENCES:
patent: 5991825 (1999-11-01), Ng
patent: 6515819 (2003-02-01), Schmidt et al.
patent: 6763430 (2004-07-01), Camp
U.S. Appl. No. 09/638,253, entitled “Space-Efficient Expected Access Time Algorithm for Hard Disk Drive Command Queue Ordering,” filed Aug. 14, 2000, by Espeseth et al.
U.S. Appl. No. 10/215,403, entitled “Method and System for Efficiently Calculating and Storing Expected Access Time Information for DASD,” filed Aug. 8, 2002, by Hall.

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