CD-ROM average access time improvement

Details CD-ROM average access time improvement CD-ROM average access time improvement

Filed on

1996-06-17

Date issued

1998-06-09

Examiner

Chan, Eddie P.

Other Related Categories

395445, 395465, G06F 1208

Type

Patent

Status

active

Patent number

057649456

Description

ABSTRACT:
A cache for improving access to optical media includes a primary cache comprising RAM and a secondary cache comprising a portion of hard disk memory. Multiple aspects of the invention are defined: (1) Cache data discrimination: Discrimination methodology is implemented for determining when data should not be cached. Under certain conditions, caching of data is less likely to improve access time. (e.g., when the transfer rate is already exceeding a critical sustained throughput rate; when an estimated time to complete a CD-ROM data request is within a specific percentage of the estimated time to complete a hard drive disk request). (2) Secondary cache fragmentation avoidance: To keep the access time to secondary cache faster than the access time to the optical media, fragmentation of the secondary cache (i.e., hard disk) is minimized. To do so, constraints are imposed: (i) an entire CD-ROM request is stored in contiguous sectors on the hard drive; (ii) sequential CD-ROM requests to adjacent sectors of CD-ROM are concatenated on the hard drive; (iii) data redundancy is permitted). (3) Alternative update methodologies: Cache updates are performed in sequence or in parallel to primary and secondary cache depending upon the embodiment. (4) Data integrity: Integrity of data stored in non-volatile secondary cache is maintained for a substantial portion of secondary cache through power failures, shutdowns and media swaps.

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