Cache management using multiple cache memories and favored volumes with multiple residency time multipliers

Abstract

A method for demoting a selected storage element from a cache memory includes storing favored and non-favored storage elements within a higher performance portion and lower performance portion of the cache memory. The method maintains a plurality of favored LRU lists and a non-favored LRU list for the higher and lower performance portions of the cache memory. Each favored LRU list contains entries associated with the favored storage elements that have the same unique residency multiplier. The non-favored LRU list includes entries associated with the non-favored storage elements. The method demotes a selected favored or non-favored storage element from the higher and lower performance portions of the cache memory according to a cache demotion policy that provides a preference to favored storage elements over non-favored storage elements based on a computed cache life expectancy, residency time, and the unique residency multiplier. A corresponding storage controller and computer program product are also disclosed.

Description

BACKGROUNDField of the Invention[0001]This invention relates generally to data processing and data storage systems, and more particularly to systems and methods for improving cache memory performance and management within a storage system.Background of the Invention[0002]In the fields of data processing or data storage systems, a “cache” or “cache memory” typically refers to a small, fast memory or storage media used to store data or instructions that were accessed recently, are accessed frequently, or are likely to be accessed in the future. Reading from or writing to a cache memory is typically less expensive, in terms of access time and / or resource utilization, than accessing other memory or storage devices. Once data is stored in cache memory, it can be accessed in cache memory instead of re-fetching and / or re-computing the data, saving time and system resources, and improving system performance.[0003]Cache memories can be implemented as multi-level caches. For example, a cache ...

AI Technical Summary

Benefits of technology

The invention provides a method for promoting and demoting storage elements within a cache memory that includes different types of memory. The method maintains separate lists for favored and non-favored storage elements based on their residency time in the cache. The method also keeps track of the number of times a storage element has been accessed and uses a cache demotion policy to select which storage elements should be demoted. The technical effects of the invention include improved performance and efficiency of cache memory usage.

Problems solved by technology

SCM is much cheaper than DRAM but has higher latency than DRAM (microseconds compared to nanoseconds).

Because SCM uses flash memory to store data, SCM exhibits some of the same limitations and deficiencies as flash memory, such as write-cycle limits and issues with data fragmentation.

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