Operating System - OpenVMS
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VMS Image backup

 
Hoff
Honored Contributor

Re: VMS Image backup

>...To make your BACKUP faster, set the process quota values as described in the System Managerâ  s Manual...

And if you're already there and have your quotas set to the recommendations, then the next step is usually faster hardware; finding the bottleneck and removing it. That's usually the input disk drive, though can be the bus or the target tape drive.

Correctly-tuned BACKUP is generally limited by how fast it can get data off a disk (eg: fragmentation), within about 10% or so of the theoretical maximum bandwidth of the slowest device in the I/O path.

If you need yet faster, an alternative approach (and described over in the shadowing manual) involves splitting a member off a shadowset, then backing that member up. That's a moment-in-time backup, though the snapshot might not be entirely consistent if you catch any multi-part write I/O activity in flight.
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P Muralidhar Kini
Honored Contributor

Re: VMS Image backup

>> Correctly-tuned BACKUP is generally limited by how fast it can get data
>> off a disk (eg: fragmentation),
You can degrament the disk on a regular basis so that the disk is not badly
fragmented. You can use DFO for the defragment operation and may be
schedule it to run when there is less load, say once a week or any other
frequency that suits best based on the disk usage.

Regards,
Murali
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