Disk drive cache system using a dynamic priority sequential stream of

Abstract

A magnetic disk drive with a caching system includes an intelligent interface to communicate with a host, a magnetic disk and a cache memory to buffer data transferred to and from the host. The caching system maximizes drive performance based on past access history. The caching system alters execution of commands by coalescing commands or executing internal commands in parallel. The caching system anticipates data requests by using a prefetch to store data that may be requested. The caching system divides the cache memory into segments to store multiple streams of data. The number of segments may be continuously adapted according to the types of access to maximize performance by maintaining a segment for each sequential stream of data. The caching system uses a dynamic priority list to determine segments to maintain and discard. Each segment is monitored to determine access types such as sequential, random, and repeating. The access type determines the amount of data to prefetch and to save, including a minimum and maximum prefetch. The caching system may prescan the cache memory during prefetch to alter the prefetch amount in response to a command request. The caching system may wait for a cache memory access that has not yet occurred. An initiator changes the caching parameters though a mode page.