US 5,692,155 AGranted

Method and apparatus for suspending multiple duplex pairs during back up processing to insure storage devices remain synchronized in a sequence consistent order

AssigneeInternational Business Machines Corporation

InventorsJames Lincoln Iskiyan, Robert Frederic Kern, William Frank Micka, Robert Wesley Shomler

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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.

Claims17

Dependent claims

In a data storage system capable of writing records and record updates and copying said records and record updates for backup purposes, said data storage system including a host processor running an application generating records and record updates, a first duplex pair having a primary data storage device and a secondary data storage device, a second duplex pair having a primary data storage device and a secondary data storage device, a storage controller coupled between said host processor and said first and said second duplex pairs, a method for suspending said first and said second duplex pairs while copying said records and record updates such that said secondary data storage devices of said first and said second duplex pairs remain synchronized in a sequence consistent order comprising steps of:

quiescing said first duplex pair by said storage controller in response to an initial quiesce command from said application to inhibit writing future records and record updates from said application to said primary data storage device of said first duplex pair, wherein said quiescing does not halt said application running in said host processor;
quiescing said second duplex pair by said storage controller in response to a subsequent quiesce command from said application to Inhibit writing future records and record updates from said application to said primary data storage device of said second duplex pair and to synchronize records and record updates copied to said secondary data storage device of said first and second duplex pairs in a sequence consistent order, wherein said quiescing does not halt said application running in said host processor;
suspending said first and second duplex pairs by said storage controller receiving a suspend command from said application to inhibit copying, by said storage controller to said secondary data storage device of said first and second duplex pairs, of records and record updates transmitted from said application to said primary data storage device of said first and second duplex pairs;
and
signalling said application by said storage controller that said first and second duplex pairs are suspended and subsequent records and record updates can be written to said primary data storage device of said first and second duplex pairs without copying said record to said secondary data storage device of said first and second duplex pairs.

2 more elements

In a data storage system providing data duplexing, said data storage system including a host processor running an application, a first duplex pair having a primary data storage device and a secondary data storage device, a second duplex pair having a primary data storage device and a secondary data storage device, a storage controller coupled between said host processor and said first and said second duplex pairs, said application generating records and record updates and issuing a quiesce duplex pair and a suspend duplex pair command, said primary data storage device for storing said records and record updates, said secondary data storage device for storing copies of said records and record updates, said storage controller for suspending said first and said second duplex pairs such that said secondary data storage devices remain synchronized in a sequence consistent order comprising:

a storage path for directing records and record updates between said host processor and said first and said second duplex pairs, said storage path quiescing said first and second duplex pairs in response to said quiesce duplex pair commands from said application, such that said application is not halted within said host processor, to inhibit writing future records and record updates from said application to said primary data storage devices of said first and said second duplex pairs, said storage path further suspending said first and second duplex pair in response to said suspend duplex pair commands from said application such that said records and record updates are copied to said secondary data storage devices of said first and said second duplex pairs and synchronized in a sequence consistent order;
and
a memory coupled to said storage path for storing said records and record updates to be copied to said secondary data storage device of said duplex pair.

A data storage system comprising:

a host processor running an application generating a plurality of record updates, said host processor issuing a quiesce duplex pair command and a suspend duplex pair command;
a channel coupled to said host processor;
a first and second duplex pair, each having a primary data storage device and a secondary data storage device, said primary data storage device for storing said plurality of record updates and said secondary data storage device for storing a copy of said plurality of record updates;
a storage controller coupled to said host processor by said channel and further coupled to said first and said second duplex pair, said storage controller comprising:
a memory for initially storing said plurality of record updates transferred from said host processor;
and
a storage path coupled between said channel and said first and said second duplex pairs, said memory further coupled to said storage path, said storage path directing movement of said plurality of record updates between said host processor and said primary data storage device through said memory, said storage path copying said plurality of record updates to said secondary data storage device, said storage path quiescing said first and second duplex pairs in response to said quiesce duplex pair commands from said application, such that said application is not halted within said host processor, to inhibit future writing of said plurality of record updates from said application to said primary data storage devices of said first and said second duplex pairs, said storage path further suspending said first and second duplex pair, in response to said suspend duplex pair commands from said application, such that said plurality of record updates copied to said secondary data storage devices remain synchronized in a sequence consistent order.

4 more elements

Dependencies are inferred from the claim text.