How to improve the space utilization of dedup-based PCM storage devices?

Abstract

There is a growing demand to introduce more and more intelligence to storage devices in recent years, especially with the rapid increasing of hardware computing power. This paper targets on essential design issues in space utilization for dedup-based non-volatile phase-change memory (PCM). We explore the adoption of data duplication techniques to reduce potential data duplicates over PCM storage devices to provide more storage space than the physical storage space does. Among various data deduplication techniques, variable-sized chunking is considered in less cost-effective PCM-based storage devices because variable-sized chunking has better data deduplication capability than fixed-sized chunking. However, in a typical system architecture, data are written or updated in the fixed management units (e.g., LBAs). Thus, to ultimately improve the space utilization of PCM-based storage device, the technical problem falls on (1) how to map fixed-sized LBAs to variable-sized chunks and (2) how to efficiently manage (i.e., allocated and deallocate) free PCM storage space for variable-sized chunks. In this work, we propose a free space manager, called container-based space manager, to resolve the above two issues by exploiting the fact that (1) a storage system initially has more free space to relax the complexity on space management and (2) the space optimization of a storage system can grow with the time when it contains more and more data. The proposed design is evaluated over popular benchmarks, for which we have very encouraging results.