RAID6L: A log-assisted RAID6 storage architecture with improved write performance

The RAID6 architecture is playing an increasingly important role in modern storage systems due to its provision of very high reliability. However, its high write penalty, because of the double-parity-update overheads upon each write operation, has been a persistent performance bottleneck of the RAID6 systems. In this paper, we propose a log-assisted RAID6 architecture, called RAID6L, to boost the write performance of the RAID6 systems. RAID6L integrates a log disk into the traditional RAID6 architecture, and alleviates its write penalty by simplifying the processing steps to service a write request. On the other hand, RAID6L also guarantees that the accelerated RAID6 systems can still recover from double disk failures. The Parity Logging scheme was originally proposed to accelerate the XOR based RAID5, and we propose a method to make it also applicable to the Reed-Solomon based RAID6. We present a detailed comparison between RAID6L and Parity Logging, and show that RAID6L has several advantages over Parity Logging. Experimental results show that RAID6L significantly increases the data transfer rate and decreases the request response time when compared with the traditional RAID6 and Parity Logging systems.