Patent
1995-04-19
1997-11-25
Chan, Eddie P.
39518204, G06F 1300
Patent
active
056921551
ABSTRACT:
A data storage system atomically suspends multiple duplex pairs across either a single storage subsystem or multiple storage subsystems. The duplex pairs are suspended such that the data on the secondary DASDs of the duplex pairs is maintained in a sequence consistent order. A host processor in the data storage system running an application generates records and record updates to be written to the primary DASDs of the duplex pairs. The storage controller directs copies of the records and record updates to the secondary DASDs of the duplex pairs. Sequence consistency is maintained on the secondary DASDs by quiescing the duplex pairs and then suspending the duplex pairs with change recording. Quiescing the duplex pairs allows any current write I/O in progress to complete to the primary DASD. The storage controller then locks out any subsequent write I/O from the host processor by raising a long busy signal to such subsequent write requests. Suspending the duplex pairs with change recording directs the storage controller to mark the physical address of the primary DASD which the application in the host processor updates between the time the duplex pair is suspended and then is reestablished.
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Iskiyan James Lincoln
Kern Robert Frederic
Micka William Frank
Shomler Robert Wesley
Chan Eddie P.
International Business Machines - Corporation
Kim Hong C.
Sullivan R. M.
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