International Business Machines Corporation

Roger G Cath

Ian David Judd

Patrick Allen Buckland

Gordon J Cockburn

William A Short

A data storage subsystem and method for transferring data from a storage subsystem to a connected host data processing system are described. The subsystem comprises a device controller connected to one or more direct access storage devices e.g. disk drives. The host data processing system issues data transfer commands to the subsystem to initiate transfer of data between the host processing system and the device(s) associated with the data storage subsystem. Read/write data is transferred directly from device to host via a buffer controller. For a read operation, the read command from the host data processing system specifies the data to be transferred and the start address in host memory to which the data should be sent. The device controller of the data storage subsystem is capable of respecifying or amending the start address specified by the host in the rad command. This provides a performance bonefit for split data transfers. In addition, if an error occurs during a read operation, the device controller of the data storage subsystem can specify the host address to which the replacement data should be sent.

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Eastleigh, United Kingdom

Roger G Cath