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On 03/06/11 22:54, Andrew Schulman wrote:
>> I'm about to set up a remote backup server to backup images of virtual
>> machines.
>>
>> What would the data transfer be (after the intial "sneakernet" transfer)
>> when a remote image gets updated/changed? Filename would not change, but
>> contents and maybe size would.
> 
> An entire new copy of that day's VM disk image will be created each day.
> BackupPC doesn't compute or store diffs, if that's what you were thinking.
> All it can do is store a new copy of the entire disk image, if even one
> byte has changed in it.
> 
> This is likely to be infeasible unless you have a very large amount of
> storage and transfer bandwidth.  When I set up BackupPC I quickly realized
> that the daily VM images were going to consume all of my backup storage in
> a very short time, so I added rules to exclude all of them.
> 
> The fallback strategy is to configure each VM internally as a BackupPC
> client.

Great suggestion, backing up the VM's as if they were normal clients...
Another option that I do sometimes (not just with VM images, but also
dumps/exports from SQL server or mysql or other proprietary software, is
to get the single large file and split it into a directory with a number
of smaller files. Then let backuppc backup this directory. Thus, in the
normal case where most of the parts don't change, then most of the parts
don't consume extra space in backuppc. Also, I found backups to be
faster, and the rsync protocol to be more efficient (both in bandwidth
consumption and run time) by doing it this way.

Your mileage might vary... one thing I do suggest is to monitor in some
way that your directory of files is actually being updated with the most
recent backup.... This can catch you unawares if your split script is
failing :)

Regards,
Adam

- -- 
Adam Goryachev
Website Managers
www.websitemanagers.com.au
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