Use of the VM:Tape command exit provides a means to automagically swap the 
mount command volsers in any order you desire.  Works great for us after most 
operators moved to the remote campus.  Now, without swapping onsite and offsite 
tape vaults, read mounts are swapped to the remote site where tape operators 
have moved.  For D.R. the command exit automatically detects which campus we're 
running in, and mount the tape at that campus.  Cool!

Mike Walter
Hewitt Associates


----- Original Message -----
From: "Mark Wheeler" [EMAIL PROTECTED]
Sent: 06/06/2008 06:48 PM EST
To: [email protected]
Subject: Re: VM:Backup: Twinning Tapes to Remote Tape Unit



Mark Llewellyn wrote on 06/05/2008 03:12:50 PM:
>
> Our other option is to simply run two backup jobs, one to the local drive

> and one to the remote, but that effectively doubles the hit of the backup

> jobs.

The (I/O) performance hit on this might not be as high as you think. If you
ran the two backup jobs concurrently (allowed by VM:Backup), the second job
(they won't be exactly in sync) can benefit by "drafting" (for all you
NASCAR fans) behind the other through the magic of minidisk caching. In
such a scenario, VMBACKUP should probably have OPTION NOMDCFS in its
directory definition.

This is also assuming that:
1) one job doesn't get too far out of sync with the other (ex remote tape
drives much slower than local)
2) you have sufficient storage for MDC, to make it worthwhile as a tradeoff
for I/O.

That said, I would still avoid this option. Restores will be based
(generally) on the "last" backup in the catalog, which will likely be
associated with the slowest-running backup job. Meaning tapes at the remote
(aka "slowest") location will be used. You could adjust for this (could
casual users?), but it would be a PITA. Alternatively, you could configure
two VMBACKUP machines (ex VMBACKUP and VMBREMOT), but that wouldn't be
pretty either.

Best regards,

Mark Wheeler, 3M Company



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