Research And Implement Of Online Capacity Expansion In RAID System

Since the concept of RAID (Redundant Arrays of Inexpensive Disks) had been made by David Patterson in 1988, RAID technology developed and was widely used in the current large-scale storage systems. With the explosive growth of information and the emergence of multimedia applications, the RAID systems are often lack of storage capacity, the traditional way which uses new arrays instead of the old one often resulted in service disruptions, and it cost more. In this situation, the RAID system must provide the function of online capacity extension. How to provide the RAID system an online capacity extension which is high efficient and smaller impact to normal service is becoming an important subject.The core issue of online capacity expansion for RAID system is the selection of the data migration algorithm, the online RAID capacity expansion of existing products mostly use simple data migration algorithm, that is, to maintain the original layout of the data in the same way. Analysis of the advantages and disadvantages of the simple data migration algorithm, five evaluation criteria are proposed for data migration algorithm, on the basis of this five evaluation criteria, an efficient, feedback-based, group and field districted data migration strategy is proposed.An online capacity expansion system for RAID is designed using feedback-based, group and field districted data migration strategy. The system not only can achieve normal function of online extension, but also a lot of flexible management functions.After comparing the existing way of the RAID capacity expansion, six performance targets for high performance RAID capacity expansion system are proposed. Using the six performance targets assess the online capacity expansion system for RAID, demonstrates that the expansion system have a good performance.