Study Of Optimization Method Of Virtual Mirror System On Mass Hierachical Optical Storage

Virtual mirror optical storage system using magnetic storage medium is the important way to enhance the performance of mass optical storage. So the I/O performance of vitual mirror system is one of the key factors of the performance for the whole hierachical mass storage system. The optimization method has been studied in this dissertation. The main contents of the dissertation are as follows:Main contemporary I/O transfer protocols are analyzed and compared, especially SCSI protocol and ATA protocol which are the most widely used standards in storage markets. Through the study of the contrasts between SCSI disk and ATA disk on I/O responding and controlling features, ATA disk is selected as storage unit in the subsystem as a result that ATA disk is superior to SCSI disk at control realization and single device accessing.Factors of cache performance are analyzed, including cache size, cache unit size, and strip size. The detail is studied of different cache scheme implementation depending on different sorts of I/O requests. And the parallel cache strategy is given out. The model of cache occupancy rate is established using Markov process and a method to settle small-write problem of RAID5 is proposed.A queue network model of subsystem is constructed by the research using stochastic queue theory. Firstly, the random accessing model of single ATA disk is studied, and the related parameters are measured. Then, I/O responding time is analyzed of isomorphic synchronous disk array. Furthermore, a whole detailed model is described of the disk array with cache. Finally, the testing results are given out through the simulation.The implementation project of the subsystem is described. Finally, we give out the testing results of subsystem in bottom I/O measurement.