Software Orchestrated Flash Array

Abstract

Because of the explosive growth of flash disk usage in portable computers and mobile devices, building data center storage systems using these commodity flash disks has become a compelling option. A vanilla approach to integrating multiple flash disks into a storage system is to put them under the control of a RAID controller. However, this approach incurs longer write latency than necessary and leads to reduction in the overall system lifetime. This paper describes a log-structured flash array architecture called SOFA (Software Orchestrated Flash Array), in which the flash translation layer (FTL) sits on top of rather than below disk array management logic, and is judiciously partitioned between a central control server and the on-disk controllers. By directly managing the resource usage in individual flash disks, SOFA is able to avoid the load and wear imbalance problems associated with existing flash disk array systems. Empirical measurements of an industrial-strength SOFA prototype show it could execute more than 7,000 random 8KB writes per second per SATA-2 flash disks, and sustains the same per-disk random write performance when the system holds up to 24 flash disks.