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Statistical Analysis of Disk Drives Performance with Application Directed Prefetching Approach

Javed hussain, Ilyas Khan

Modern magnetic disks are, as is well known, dramatically slower at random reads than sequential reads. Technological progress has exacerbated the problem; disk throughput has increased by a factor of 60 to 85 over the past twenty-five years, but seek times have decreased by a factor of only 15. Disks are less and less like random access devices in terms of performance. Although flash memory reduces the cost differential of random accesses, disks continue to offer vast amounts of inexpensive storage. For the foreseeable future, it will remain important to optimize the performance of applications that access disk like devices that is, devices with much faster sequential than random access. The best solution to this performance problem is to avoid critical path disk access altogether and reading unneeded data as sequential access and discarding it later.