Online availability upgrades for parity-based RAIDs through supplementary parity augmentations

  • Authors:

  • Lei Tian;Qiang Cao;Hong Jiang;Dan Feng;Changsheng Xie;Qin Xin

  • Affiliations:

  • Huazhong University of Science, China and Technology/University of Nebraska-Lincoln, Lincoln, NE;-;University of Nebraska-Lincoln, Lincoln, NE;Huazhong University of Science and Technology, China;Huazhong University of Science and Technology, China;-

  • Venue:
  • ACM Transactions on Storage (TOS)
  • Year:
  • 2011

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Abstract

In this article, we propose a simple but powerful online availability upgrade mechanism, Supplementary Parity Augmentations(SPA), to address the availability issue in parity-based RAID systems. The basic idea of SPA is to store and update the supplementary parity units on one or a few newly augmented spare disks for online RAID systems in the operational mode, thus achieving the goals of improving the reconstruction performance while tolerating multiple disk failures and latent sector errors simultaneously. By applying the exclusive OR operations appropriately among supplementary parity, full parity, and data units, SPA can reconstruct the data on the failed disks with a fraction of the original overhead that is proportional to the supplementary parity coverage, thus significantly reducing the overhead of data regeneration and decreasing recovery time in parity-based RAID systems. Our extensive trace-driven simulation study shows that SPA can significantly improve the reconstruction performance of the RAID5 and RAID5+0 systems, at an acceptable performance overhead imposed in the operational mode. Moreover, our reliability analytical modeling and sequential Monte-Carlo simulation demonstrate that SPA is consistently more than double the MTTDL of the RAID5 system and improves the reliability of the RAID5+0 system noticeably.