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HP OpenVMS Systemsask the wizard |
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The Question is: I wish to configure a two- or three-node SCSI cluster which meets these criteria: - dual SCSI buses for throughput - volume shadowing for minimum application downtime during BACKUP (the shadow set is dissolved immediately prior to BACKUP then rebuilt with only one member; the other member is mounted privately for BACKUP to copy to tape) Is it possible to run host-based volume shadowing with the shadow set built from paired virtual units from a pair of HSZ RAID controllers? Each virtual unit would be a RAID 0 set. The Answer is :
What you are proposing will operate. You can build a shadow set from
the virtual units of the HSZ controllers, so long as the MAXBLOCKS and
volume geometry of the virtual units match exactly.
There are two caveats:
o make sure you completely stop your application(s) before dissolving
shadow sets -- this may require application shutdown, and is best
handled by dismounting the entire shadow set. This application-level
quiescence is necessary to make sure application data is consistent
and correct. OpenVMS will guarantee the integrity of the file system
when shadow sets are dissolved. OpenVMS cannot guarantee the
integrity of the data the file system contains -- this consistency
is the responsibility of the application.
o make sure you use at least OpenVMS Alpha V7.2-1, the minimum version
for multipath SCSI support. Consider adding additional controllers
and using multiple paths to the HSZ controllers with Multipath enabled.
This will provide you with additional availability should a controller
or a SCSI cable fail or become disconnected.
Also note that splitting shadow sets increases your exposure to bad blocks.
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