Patent ID: 6880043

Claim:
A disk drive for servicing host commands, comprising: cache memory having a plurality of memory clusters for caching disk data of disk sectors identified by logical block addresses; and a cache control system including a tag memory having a plurality of tag records, each tag record for defining a variable length segment of the memory clusters for caching disk data for a range of logical block addresses and each tag record for indicating the range of logical block addresses, a scan engine only usable for scanning the tag records having means for receiving a range of logical block addresses associated with a host command, means for reading the ranges of logical block addresses defined by the tag records, means for comparing the range of logical block addresses associated with the host command with the ranges of logical block addresses indicated in the tag records, means for providing scan results, based on a comparison by the means for comparing, indicating overlap between the logical block address range associated with the host command and the ranges of logical block addresses indicated in the tag records.