DVS: Dynamic Variable-Width Striping RAID for Shingled Write Disks
Disk data density improvement will eventually be limited by the super-paramagnetic effect for perpendicular magnetic recording. Of the various new technologies being explored, Shingled Magnetic Recording (SMR) exposes as the most promising one to achieve high areal density and only make little changes to the manufacturing process. At present, high-capacity SMR drives are available from Seagate and HGST. Since SMR is leading next generation disk technology and increasing SMR drives will be used in storage systems, there is a great need to look over the current RAID storage techniques based on HDDs again. In this paper, we proposed a dynamic variable-width striping RAID (DVS-RAID) for SMR drives to reduce the parity updating cost. DVS-RAID never overwrites the old data, but always constructs a new full or partial stripe (variable-width stripe), and writes to the SMR drives through appending. In addition, taking the access characteristics of SMR drives into consideration, we present a new write cache management that exploits both spatial and temporal localities. The experiment with six real-world traces demonstrates that DVS- RAID exhibits a slightly lower performance than HDD- based RAID on update intensive workloads. However the performance of DVS-RAID is better than HDD-based RAID with sequential access, read-dominated workloads or workloads with rarely update.