The Evaluations of 2P-3D Orthogonal RAIDs in Virtual Large-Scale Disks

Abstract

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 fault tolerant RAID is important. In the previous work we proposed Mesh RAID that is 3 fault tolerant orthogonal RAID. And, we implemented Mesh RAID using VLSD. Mesh RAID is a hierarchical RAID that shares elemental disks. The structure of hierarchical RAID is tree but the structure of Mesh RAID is DAG(Directed A cyclic Graph). Mesh RAID is not tolerant of only disk fault but also tolerant of string fault. Furthermore, in hierarchical RAID, the larger the number of layers is, the higher the reliability of the system. In Mesh RAID, increasing the layers is equivalent to increasing the dimensions. In the previous work, we proposed and implemented MeshRAID3D and MeshRAID2P. MeshRAID3D has 3 layers of elementary RAID. In MeshRAID2P, each elementary RAID has 2 parities and realizes 2FT. So, we consider 2P-3D Mesh RAID(MeshRAID3D2P), which is combined with MeshRAID2P and MeshRAID3D. Theoretically, MeshRAID3D2P achieves 26FT. In this paper, we describe MeshRAID3D2P in detail and prove whether it is really 26FT or not.