Research On MDS Array Code In Distributed Storage System

With the rapid increasement of data in modern society,the reliability of modern storage systems is susceptible to more challenge.The method of improving the reliability of the storage system is mainly by adding redundant information,and there are two ways to achieve this goal.One is replication technology and another is erasure code technology.Replication technology is difficult to meet the requirement of mass data since they own a large storage overhead.Therefore,erasure code is often used for modern storage technology to improve data reliability and usability.Among the erasure code technologies,the array code is a good one,which is easy to implement for holding a simple XOR operation.The theoretically optimal storage utilization can be achieved when the array code satisfies the Maximum Distance Seperable(MDS)property.In this paper,the MDS array code is studied.Firstly,the parameters of Blaum-Bruck-Vardy(BBV)Codes are considered,and under the condition of existing lower bound,the research work of optimizing the existing lower bound is carried out.What's more,I study the extension of EVENODD code,EVENODD(p,3)code,focusing on it's repair problem when there is some failure.Since the single disk failure is more common,I pay attention to the disk reads for it's single information disk failure recovery.At last,some work has been done towards the disk reads for single information disk failure recovery of EVENODD(p,4)code and RDP(p,4)code.In this paper,I study the array code,focusing on the parameters' condition to meet the MDS property and the repair problem of the extension of EVENODD and RDP code.The main work of this paper is as follows:1.Improve the parameters' condition to meet the MDS property for BBV code with more than 8 parity columns.The result shows that the lower bound on p in this paper is better than the exiting one.Therefore,a tighter MDS condition is presented.2.Deduce a lower bound on disk reads and give out a recovery scheme for single information disk failure recovery of EVENODD(p,3)code.The number of disk reads in this recovery scheme is less than the minimum number of disk reads for single information disk failure recovery of EVENODD code.3.Study on the disk reads for single information disk failure recovery of EVENODD(p,4)code and RDP(p,4)code.Make comparison between EVENODD code,EVENODD(p,3)code and EVENODD(p,4)code.What's more,make comparison between RDP code,RDP(p,3)code and RDP(p,4)code.