Performance Evaluation of 2FT RAID

Recently, there has been increased demand for large-scale online storage for clouds, life logs, and other applications. Previously, we developed the VLSD (Virtual Large-Scale Disks) toolkit for constructing large-scale online storage, using RAID to realize reliable storage. RAID5 is commonly used, but it is not adequate for large-scale online storage because it provides only level 1 fault tolerance (1FT). Currently, many storage appliances employ more than 1FT RAID, such as RAID6. However, there are several RAID classes with greater tolerance than 1FT. In previous works, we developed another 2FT RAID, RAID4PQ, which is similar to RAID6 in the sense that it uses P+Q parities. However, it differs from RAID6 in that it has dedicated double parity. Furthermore, RAID RDP is also a 2FT RAID, in which the 2 parities are row and diagonal parities (RDP). In this paper, we implement these RAID types as VLSD classes and compare their performance.