Dasd I/O caching method and application including replacement policy minimizing data retrieval and storage costs

摘要

The performance of a DASD having a data cache and at least one set of R/W heads is improved by implementing a replacement policy which, upon determining that a request for data in the DASD requires replacement of a data in a data cache buffer, selects cache data corresponding to data which is cheapest to retrieve from the DASD in view of a location of the DASD R/W heads and replaces the selected cache data with the requested data, thus keeping the cache filled with data which is least expensive to retrieve from the DASD. Data in the DASD is updated from the cache when it is inexpensive.