Research Of Erasure Code For Raid System

The rapid development of computing and network technology led to an explosionof digital information growth. Information technology has entered an era with storagetechnology as the core, and put forward increasingly high demand on the reliability ofstorage systems. RAID was once an effective means to solve this problem. But withthe emerging of large-scale storage systems and high-density large-capacity disks, thetraditional RAID technology has been difficult to ensure the reliability of data. Erasurecode in disk array is a feasible and effective way to increase system reliability.The main work and achievements contained in this thesis are as follows:1. Traditional RAID technique were reviewed, and The development, principle, struc-ture and the current challenges of traditional RAID technology are summarized.This paper introduces the basic principle of erasure code. The encoding principle,performance and reliability of three practical erasure code technology is analysed,and based on their existence deficiency, new code research direction is proposed.2. We have designed a new MDS array erasure code, named DA-Code, which cantolerate double disk failures, and strictly proved that this code have distance of 3.Detailed data reconstruction algorithms of single disk failure and double disk fail-uresweregivenrespectively. DA-Codehasseveralindependentdatareconstructionchains. So, data reconstruction can be accelerated by parallel processing. We useda large number of simulation data and random fault model to verify the correctnessof DA-Code and its algorithms.3. Atlast,weanalyzedDA-Code'sfault-toleratingperformance. Itreachestheoptimalvalue of double-disk-failure-tolerating MDS array erasure code at all four aspects:encoding complexity, update (small write) complexity, decoding (data reconstruc-tion) complexity and storage efficiency, and has excellent load balance feature. Weused detailed data to show DA-Code's advantages comparing with Reed Solomoncode, EVENODD code and RDP code. As a kind of vertical code, DA-Code breaksthe prime limit on the disk number, and has good flexibility in the practical appli-cation. The verification based on Markov model shows that, compared with the existing coding technology, DA-Code can improve the reliability of disk array ob-viously.