Storage Controller and Method for Managing Modified Data Flush Operations From a Cache

摘要

A storage controller maintaining a cache manages modified data flush operations. A set-associative map or relationship between individual cache lines in the cache and a corresponding portion of the host managed or source data store is generated in such a way that a quotient can be used to identify modified data in the cache in the order of the source data's logical block addresses. The storage controller uses a collision bitmap, a dirty bit map and a flush table when flushing data from the cache. The storage controller selects a quotient and identifies modified cache lines in the cache identified by the quotient. As long as the quotient remains the same, the storage controller flushes or transfers the modified cache lines to the data store. Otherwise, when the quotient is not the same, the data in the cache is skipped. A linked list is used to traverse skipped cache lines.

主权项

1. A method for managing modified data flush operations from a cache, the method comprising:
defining a relationship between a cache line in a data store exposed to a host system and a location identifier associated with an instance of the cache line, the relationship responsive to a variable and a constant; maintaining a set of bitmaps that identify cache lines that include modified data; identifying a quotient responsive to the variable and the constant; using the quotient to flush a first associated cache line with modified data; consulting the set of bitmaps to identify a next subsequent cache line that includes modified data; verifying that a present quotient corresponds to a source logical disk for a present cache line,
when the present quotient corresponds to the source logical disk,flushing the present cache line;otherwise, recording an identifier for the present cache line; incrementing a cache line index; and repeating the verifying, flushing and incrementing.