[PVE-User] WG: difference b/w backup types

Matthew Caron Matt.Caron at sixnet.com
Wed Sep 28 17:30:29 CEST 2011

On 09/28/2011 11:21 AM, Alain Péan wrote:
> Hi Jeremiah,
> Just a question, just to know what is the best policy. Do you use
> BackupPC to backup the image files inside the host, or the files inside
> the VM ? The image files are big files, that change at least slightly
> (logs, updates...), so backupPC needs to backup the whole (big) file
> each time.

Not necessarily. BackupPC uses rsync, which has a differential changes 
algorithm, so it only sends the regions of the files which changed over 
the wire. From the manpage:

It is famous  for  its delta-transfer  algorithm,  which  reduces the 
amount of data sent over the network by sending only the differences 
between  the  source  files and  the  existing  files in the destination.

As long as you're not moving the original files, off of the destination 
(say, for offsite backups), this will only copy what changed.

Of course, if you want offsites, you can set up a RAID 1 mirror on your 
backup server, then pop the drive out in the morning, replace it, and 
let it rebuild, then take the one you just pulled out offsite. Of 
course, in this case I'd recommend a 3 way mirror, so that you still 
have redundancy while the third disk is rebuilding.

Matthew Caron
Build Engineer
Sixnet | www.sixnet.com
O +1 518 877 5173 Ext. 138
F +1 518 602 9209
matt.caron at sixnet.com

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