Browse Prior Art Database

Managing Storage Subsystems

IP.com Disclosure Number: IPCOM000040982D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Dube, JT: AUTHOR

Abstract

Performance of a string of direct access storage devices (DASD) is matched to the access demands. When access demands are low, a buffer area on the DASD is assigned to receive all data from a connected host. This eliminates seeks and allows data to be recorded more quickly.

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Managing Storage Subsystems

Performance of a string of direct access storage devices (DASD) is matched to the access demands. When access demands are low, a buffer area on the DASD is assigned to receive all data from a connected host. This eliminates seeks and allows data to be recorded more quickly.

The DASD subsystem has an "always ready" extra surface on a given one of a plurality of DASDs which may be connected together by a daisy chain or to a radial connection to a common controller. Since the extra surface is always ready, seek requirements and latency times are eliminated for greatly reducing the write commit time of the channel. Later, when the other DASDs are not busy, the "always ready" surface stored data is transferred to the other DASDs, similar to cache storage. In accordance with the invention, retentive storage is immediately provided by the "always ready" surface.

An enable switch controls access to the "always ready" surface. The enable switch is turned on when there is a low access rate to the various DASDs. With the access rate high, the enable switch is turned off such that the connected host processor accesses the DASD directly because writing to the "always ready" surface only increases demand on the system without decreasing response time. The demand threshold for controlling the enable switch is determined by a counter and a timer. When the number of DASD accesses exceeds a preset limit in the time period allocated, then the "always rea...