An Alternative Implementation of 3FT RAID in Virtual Large Scale Disks

Recently, the demand of low cost large scale storages increases. We developed VLSD (Virtual Large Scale Disks) toolkit for constructing virtual disk based distributed storages, which aggregate free spaces of individual disks. However, in order to construct large-scale storage, more than or equal to 3 faults tolerant RAID is important. In the previous work we proposed Mesh RAID that is 3 faults tolerant orthogonal RAID. And, we implemented Mesh RAID using VLSD. Mesh RAID is not tolerant of only disk fault but also tolerant of string fault. In addition, we also proposed Composite RAID, which is an easy implementation of complex RAID system by combining VLSD classes. We also implemented Composite RAID based Mesh RAID. In this paper, we propose another implementation of Mesh RAID based on Alternate Disk, which chooses any implementation from all implementations dynamically. This implementation has simple structure and good performance.