Method and system for estimating minumun requirements on a cache in a

Abstract

Methods and systems are disclosed which utilize Little's law to improve cache management in a computer based storage system in which the cache is a partitioned or non partitioned write-back cache. In a first aspect, a method and system for managing a write-back cache in a computer based system to accommodate for deferred write operations is disclosed. The method .and system comprises determining an average cast out delay for a cache entry. In a second aspect the method and system comprises utilizing the average castout delay for estimating the number of dirty cache entries which will be needed by the cache if the write operations rate and the average cast out delay does not change significantly. In a third aspect, a method and system for managing a partitioned and prioritized cache in a computer based system to provide sensitivity to a local maximum is disclosed. The method and system comprises determining an average residency time for a cache entry in the cache and then determining the minimum number of clean pages which should be made available to a particular cache partition based upon that average residency time. In yet another aspect the above aspects can be combined to estimate the minimum requirements on the cache to ensure that a cache management system operates in an efficient manner.