Non-interfering seek behavior modification for improved hard drive performance

摘要

Upon receiving a read command, a disk drive moves a read head to target data and reads the data into a read buffer. In an action called “prefetching”, the drive continues to read nearby data into the read buffer which doubles as a data cache. When another I/O command is present and must be serviced, prefetching is preempted thereby reducing the data read into the cache. Moving the head from the current I/O command to the next I/O command creates a delay comprising two components: seek time and rational latency. Based on the relative values of these components, a time period, less than the entire delay period, is calculated in which prefetching will continue. By continuing prefetching instead of preempting it, the likelihood of cache hits is increased because more data is available in the read buffer. Furthermore, by performing prefetching during part of the otherwise unused delay period, no performance penalty is introduced.