System for scheduling readahead operations if new request is within a proximity of N last read requests wherein N is dependent on independent activities

摘要

An improved read ahead strategy that improves the performance of a disk array subsystem. The disk controller keeps track of the last n reads to the array. If a new read request is received that is adjacent to any of the last n reads, the controller performs a look ahead read because a sequential read may be in progress. The parameter n is preferably set comparable to or greater than the number of maximum independent activites being performed by the computer system. Therefore, in a multithread system, the controller performs a readahead if any one thread is doing a sequential read.