Exploiting Redundancies and Deferred Writes to Conserve Energy in Erasure-Coded Storage Clusters

  • Authors:

  • Jianzhong Huang;Fenghao Zhang;Xiao Qin;Changsheng Xie

  • Affiliations:

  • Huazhong University of Science and Technology;Huazhong University of Science and Technology;Auburn University;Huazhong University of Science and Technology

  • Venue:
  • ACM Transactions on Storage (TOS)
  • Year:
  • 2013

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Abstract

We present a power-efficient scheme for erasure-coded storage clusters---ECS2---which aims to offer high energy efficiency with marginal reliability degradation. ECS2 utilizes data redundancies and deferred writes to conserve energy. In ECS2 parity blocks are buffered exclusively in active data nodes whereas parity nodes are placed into low-power mode. (k + r, k) RS-coded ECS2 can achieve ⌈(r + 1)/2⌉-fault tolerance for k active data nodes and r-fault tolerance for all k + r nodes. ECS2 employs the following three optimizing approaches to improve the energy efficiency of storage clusters. (1) An adaptive threshold policy takes system configurations and I/O workloads into account to maximize standby time periods; (2) a selective activation policy minimizes the number of power-transitions in storage nodes; and (3) a region-based buffer policy speeds up the synchronization process by migrating parity blocks in a batch method. After implementing an ECS2-based prototype in a Linux cluster, we evaluated its energy efficiency and performance using four different types of I/O workloads. The experimental results indicate that compared to energy-oblivious erasure-coded storage, ECS2 can save the energy used by storage clusters up to 29.8% and 28.0% in read-intensive and write-dominated workloads when k = 6 and r = 3, respectively. The results also show that ECS2 accomplishes high power efficiency in both normal and failed cases without noticeably affecting the I/O performance of storage clusters.