Warm start cache recovery in a dual active controller with cache coherency using stripe locks for implied storage volume reservations

Abstract

A storage volume reservation system and method for maintaining cache coherency amongst a plurality of caching controllers in a data storage system during a warm start cache recovery utilizing a stripe lock data structure. The stripe lock data structure is defined to maintain reservation status of cache lines within data extents that are part of a logical unit or storage volume. A battery backup unit (BBU) stores stripe lock data structure and dirty cache line data of each of the plurality of controllers during a power failure. Using the stripe lock data structure, a delay required for continued processing of I/O requests from one or more host computers following the warm start cache recovery is minimized. Without saving the stripe lock data structure, continued processing of I/O requests from one or more host computers requires reestablishing stripe locks, during the warm start cache recovery, for cache line data saved before the power failure. A computer program product for maintaining cache coherency amongst a plurality of caching storage controllers in a data storage system during a warm start is also provided which includes a computer readable medium and a computer mechanism stored thereon for implementing the inventive method and procedures thereof. Advantages of the invention include eliminating the delay required to re-establish stripe locks in order to flush dirty cache line data to a storage volume during a warm start cache recovery.