The Implementation Of Cache Management System For CD Library File

In information society, the information blows up. With the development of information construction, the devotion to storage product will be sharply increased. Combined with light, mechanical and electronic techniques, CD library is an ideal network storage product and has been applied abroadly. However, nowadays CD library has some limitations. Firstly, lots of requests for CD files appear frequently in one moment, but CD library's mechanical hand can only answer one request at one time. So the machanical hand will probably become the bottleneck. Secondly, the CD files should be copied to local hard disk before returned to clients. So the delay of answer is increased, and the quality of network service is decreased.Aiming at overcoming these above disadvantages, this paper suggests setting cluster-based cache servers before CD library. Cache servers can help to shorten the delay, and increase the lifetime of CD library. Cluster technique can enhance the system performance by balancing workload to each cache server.This paper firstly proposes the architecture of complete cache management system for CD library file, then the implementation of each function module is discussed, include: cluster-based cache servers are constructed using LAS, which is designed by network studio of WuHan University; the cluster-based cache servers connect with CD library by USB CDROM, and each cache server can automoticly mount and unmount USB CDROM; database server is selected properly to be the communication agency between the cluster cache servers and CD library; according to the feature of CD library, cache storing policy based on file types, cache replacement arithmetic and maintaining method of strong consistency are proposed. This technology is different with that of traditional proxy cache; realizing the management of CD files, include whose in cache and in CD library, and WEB management interface is also designed; designing the automatical mothod of adding CDs into and removed CDs from CD library. Finally, we perform the function test of the whole system, include the test of cache function, USB auto mount/unmount function, operation of machine hand, CD automatically added and removed function.