The Design And Implemention Of The I/O Scheduler For Shingled-recording Hard Drivers

Along with digitizing process of all things in the digital age, the amount ofinformation is at an unprecedented rate of growth, the demand for storage capacityincreases in synchronization, storage system has become a major bottleneck of theinformation system.Traditional hard disk is the main carrier of storage for theinformation. But, becouse of the effect of the superpara-magnetic, the density of themagnetic record is soon to its limit.The basic principle of shingled record is simple. When writing data, the magnetichead will overlap a part of adjacent track to make the width of effective track narrower.And the disk density could be even ten times higher than the existing, but this is at theexpense of random write performance for the price. In the existing technology conditions,we can just change a little part of the disk structure and the magnetic head, and then thistype of record will come true.The purpose of this study is to reduce the number of sectors that will be rewritten in aband. After a brief introduction of the principle of the shingled-record, a simple diskmodel was designed. And In the I/O schedule layer of the operation system, there are asorting module and an anticipatory module; next, in the block driver layer, a select modulewas given according to the position of the magnetic head, and a split-combine module wasintroduced also. At last, this algorithm will create a bitmap, both of the I/O requests whichselected and the bitmap will be packed by the download module in the end.The result of simulation shows that, the I/O Scheduler Using in theShingled-recording Hard Drivers can reduce about15%to40%of the sectors that will berewritten in a band, and decrease the loss of random write performance though themagnetic record density increases sharply.