Jaeyong Bae - Dedup-for-Speed: Storing Duplications in Fast Flash Mode for Enhanced Read Performanc

SYSTOR 2022: https://www.systor.org/2022 Abstract --------------- Storage deduplication improves write latency, earns additional space, and reduces the wearing of storage media by eliminating redundant writes. The flash translation layer (FTL) of a flash solid state disk (SSD) easily enables deduplication in an SSD by simply mapping duplicated logical pages to the same physical page. Therefore, a few deduplicating FTLs have been proposed thus far. However, deduplication of partially duplicated files breaks the sequentiality of data storage at the flash page level and results in significant degradation of the read performance. Although storage space saving, reduced flash writes and the extended lifespan are barely perceptible to users, the extended read latency is critical to user-perceived performance. In this paper, we propose a novel deduplication FTL, Dedup-for-Speed (DFS). The DFS FTL trades surplus capacity gained through inline deduplication for improved read performance by storing duplicated pages in fast flash modes, such as pseudo-SLC (single-level-cell). The flash mode of a page is determined by its degree of deduplication. Migrating duplicate pages to fast flash blocks is performed during idle intervals to minimize its interference with host-issued operations. Contrary to conventional deduplication schemes, DFS improves read performance while maintaining the aforementioned benefits of deduplication. Our evaluation of six real-world traces showed that DFS improved read latency by 16% on average and by up to 34%. It also enhanced write latency by 64% on average and by up to 82%.

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