Am 29. Oktober 2014 23:37:27 schrieb Adam Goryachev 
<mailinglists AT websitemanagers.com DOT au>:

> On 29/10/14 17:40, Dr. Boris Neubert wrote:

> >> You could in theory take a snapshot of the LV that the disk image sits
> >> on, mount the snapshot, then create the "chunks", and then umount/delete
> >> the snapshot, or any similar method, though a restore will produce an
> >> image of a "crashed" machine (like power failure crashed).
> > That's what I do except for creating the chunks. The drawback about the
> > large files is that the initial backup takes days to complete. In addition,
> > I use the snapshot feature to be able to revert to previous version of the
> > VM. I therefore keep only one full backup at all.
>
>
> I try not to keep snapshots, because they affect the performance of the
> VM so significantly. backuppc pre backup sets up the snapshot, mounts
> the VM disk, etc, then the backup is completed to backup the actual
> files of the VM, and finally the post backup umounts and deletes the
> snapshot.

Sorry, I wasn't precise. In the pre dump command, I take a snapshot of the 
underlying logical volume, mount it, back it up, and unmount and discard it 
in the post dump command. In addition, I use the snapshotting feature of 
the VM software (here: VirtualBox) to create snapshots of the VMs at 
critical points in time, e.g. before installing additional software or 
after updating the OS in the VM.

>
> Back to the images though, each day (not controlled by backuppc, just
> scheduled), the image split/etc is done. I just use the unix split, and
> also a small C program I wrote which simply slows down the IO (ie, I set
> the number of bytes/sec of STDIN that is sent to STDOUT so that I don't
> utilise all available disk IO and slow down all the running VM's), and
> write to another directory. So yes, it uses up double the space of disk
> capacity (but capacity is cheap, performance is expensive). Therefore
> when backuppc runs, it will always see one set of the split files, and
> these are mostly unchanged (even though the timestamp changes), that
> just means rsync needs to read the full file on the backup client,
> backuppc doesn't need to with checksum-cache, but since there is no
> content changed, it is very quick. I can only suggest you test this
> yourself to see the difference it can make on your systems, for me it
> was significant.
>

In my case, it's similar. The VM snapshots are static and only the 
difference images to the latest VM snapshots are changed.

> > I plan to refine this by additionally use BackupPc on certain virtual disks
> > with user data.
>
> I don't know what you mean by "use *backuppc on virtual disks* which
> also contain user data" or if you mean "use backuppc to *backup virtual
> disks with user data*"....
>
> Hopefully the second :)

Sure.

Kind regards,
Bo2



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