On 09/10 04:38 , Kenneth Porter wrote:
> (The better solution would be to use the Linux volume storage mechanism to 
> back up a snapshot, but at the time I initially set up the server, I wasn't 
> aware of this feature and didn't leave space for a snapshot partition.)

I've tried it, and abandoned it after some experimentation. 
Basically, if you try to backup a snapshot volume, it takes (as a very rough
rule of thumb) 4x as long as if you just stopped backuppc and backed up the
data pool that way. My backups were taking 2 days, and the data rate wasn't
high enough to keep the tape from 'shoeshining', which wore out tapes at a
much accellerated rate, and the amount of data change would sometimes
overflow even a very large (many tens of GB) snapshot partition, and the
load on the machine would be sky-high as disk heads ran back and forth
between writing data for backups and reading data for the tape archive
(which is a vast oversimplification I know, but you get the idea).

In short; I found it was much better to just shut down backuppc over the
weekend and archive the data pool to tape during that time.

If it was possible to replicate the data pool (DRBD?) it would be possible
to quiesce the mirror and back that up; but otherwise it's not really a good
idea to do it with just one set of disk heads. There's too much disk load
during either the normal backuppc processes, and also during an archive to
tape, for both to run at the same time. (Generally speaking, YMMV).

-- 
Carl Soderstrom
Systems Administrator
Real-Time Enterprises
www.real-time.com

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