A new differential RAID for high reliable All Flash Array

Abstract

For high I/O performance, Solid State Drive (SSD)-based all Flash arrays (AFAs) are widely employed to larger scale storage systems. However, the aging problem of SSDs limits the lifetime and reliability of AFA. In order to extend the lifetime of AFA, we designed a capacity-based differential RAID (Redundant Array of Independent Disks) scheme (CDiff-RAID). In the proposed scheme, the array is initialized by a group of SSDs with unequal capacities. The smaller SSDs suffer more erase operations and age quickly. To maintain the age differential, the worn SSDs are continually replaced by new SSDs. Compared with parity-based Diff-RAID, the age differential in our scheme is independent of workload and the time-consuming of reconstruction is greatly reduced. We also evaluated the I/O performance of CDiff-RAID using SSD simulators. The proposed scheme outperforms Diff-RAID scheme in sequential and random traces in most cases.