STORAGE CONTROL CACHE RESOURCE-MANAGEMENT - INCREASING DIVERSITY, INCREASING EFFECTIVENESS

Efficient management of cached storage control resources has been impo rtant since the introduction of cached controllers in the early 1980s, and it continues to grow more important as technology advances. The n eed for cache resource management is due to the diversity of workloads that may coexist under a given controller. Some workloads may continu ally require the staging of new data into cache memory, with almost no benefit in terms of performance; other workloads may reap major perfo rmance benefits while requiring relatively little data staging. The sh aring of resources among various workloads must therefore be controlle d to ensure that workloads in the former group do not interfere too mu ch with those in the latter. Management of cache functions is often vi ewed as the job of the host system to which the controller is attached . But it is now also possible for advanced controllers to perform such management functions in a stand-alone manner. Caching algorithms can change adaptively to match the workloads presented. This enables the c ontroller to be ported across multiple platforms without dependencies on software support. This paper surveys the variety of techniques that have been used for cache resource control, and examines the rapid evo lution in such techniques that is now occurring.