Synchronous I/O scheduling of independent write caches for an array of SSDs

Junghee Lee, Youngjae Kim, Jongman Kim, Galen M. Shipman

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Solid-state drives (SSD) offer a significant performance improvement over the hard disk drives (HDD), however, it can exhibit a significant variance in latency and throughput due to internal garbage collection (GC) process on the SSD. When the SSDs are configured in a RAID, the performance variance of individual SSDs could significantly degrade the overall performance of the RAID of SSDs. The internal cache on the RAID controller can help mitigate the performance variability issues of SSDs in the array; however, the state-of-the-art cache algorithm of the RAID controller does not consider the characteristics of SSDs. In this paper, we examine the most recent write cache algorithm for the array of disks, and propose a synchronous independent write cache (SIW) algorithm. We also present a pre-parity-computation technique for the RAID of SSDs with parity computations, which calculates parities of blocks in advance before they are stored in the write cache. With this new technique, we propose a complete paradigm shift in the design of write cache. In our evaluation study, large write requests dominant workloads show up to about 50 and 20 percent improvements in average response times on RAID-0 and RAID-5 respectively as compared to the state-of-the-art write cache algorithm.

Original languageEnglish
Article number6704732
Pages (from-to)79-82
Number of pages4
JournalIEEE Computer Architecture Letters
Issue number1
Publication statusPublished - 2015 Jan 1
Externally publishedYes


  • I/O scheduling
  • Redundant Array of Independent Disks (RAID)
  • Solid-State Drive (SSD)
  • Write cache
  • flash memory

ASJC Scopus subject areas

  • Hardware and Architecture


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