International Business Machines Corporation

Thao Bich Bui

Chan Y Ng

James C Chen

Tram Thi Nguyen

Christina Hien Tran

Michael Koester

Kevin L Miner

Richard Alan Schaeffer

In one aspect of storage device status management in accordance with the present description, a host can determine not only whether a particular volume maintained by a storage unit controlled by a storage controller is on-line with respect to another host, but also whether that volume is actually in use by another host. Accordingly, should one host determine that a volume is in use by another host, the one host can defer its use of the volume until the volume is no longer in use by another host. In this manner, conflicts which may lead to loss of data integrity may be reduced or eliminated, providing a significant improvement in computer technology. Other features and aspects may be realized, depending upon the particular application.

Storage device status management for conflict avoidance in a data storage system

A staging method and means for both device read and update write operations in which messages and commands between a storage subsystem and a fixed-block formatted RAID array emulating a variable-length record (CKD) formatted device for both read and write operations are evaluated to ascertain whether the record addressing was random and truly in record mode. If they are in that mode, then partial track staging by the RAID array control from the fixed-block formatted HDDs to a subsystem cache or the like would reduce device contention by reading and staging less than full track.

Method and means for reducing device contention by random accessing and partial track staging of records according to a first DASD format but device mapped according to a second DASD format

Method and means for reducing device contention by random accessing and

A device adapter maintains a device polling table in memory that can be dynamically changed in response to disk drive device failures and is updated with each poll so that failed devices can be quickly deleted from the table and alternate device polling mapping can be achieved. A system reconfiguration is not necessary to implement the modifications to the system processing. The device adapter is capable of a greater variety of processing tasks than is conventional, including determining cylinder head position and copying data that otherwise would be performed by a control unit.

Method and apparatus for polling and selecting any paired device in any

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Thao Bich Bui