[CentOS] KVM vs. incremental remote backups

Wed Mar 31 13:58:36 UTC 2021
Leon Fauster <leonfauster at googlemail.com>

On 31.03.21 14:41, Nicolas Kovacs wrote:
> Hi,
> Up until recently I've hosted all my stuff (web & mail) on a handful of bare
> metal servers. Web applications (WordPress, OwnCloud, Dolibarr, GEPI,
> Roundcube) as well as mail and a few other things were hosted mostly on one big
> machine.
> Backups for this setup were done using Rsnapshot, a nifty utility that combines
> Rsync over SSH and hard links to make incremental backups.
> This approach has become problematic, for several reasons. First, web
> applications have increasingly specific and sometimes mutually exclusive
> requirements. And second, last month I had a server crash, and even though I
> had backups for everything, this meant quite some offline time.
> So I've opted to go for KVM-based solutions, with everything split up over a
> series of KVM guests. I wrapped my head around KVM, played around with it (a
> lot) and now I'm more or less ready to go.
> One detail is nagging me though: backups.
> Let's say I have one VM that handles only DNS (base installation + BIND) and
> one other VM that handles mail (base installation + Postfix + Dovecot).
> Under the hood that's two QCOW2 images stored in /var/lib/libvirt/images.
> With the old "bare metal" approach I could perform remote backups using Rsync,
> so only the difference between two backups would get transferred over the
> network. Now with KVM images it looks like every day I have to transfer the
> whole image again. As soon as some images have lots of data on them (say, 100
> GB for a small OwnCloud server), this quickly becomes unmanageable.
> I googled around quite some time for "KVM backup best practices" and was a bit
> puzzled to find many folks asking the same question and no real answer, at
> least not without having to jump through burning loops.
> Any suggestions ?

As others pointed out - LVM would be a smart solution and BTW rsnapshot 
supports LVM snapshot backups.

If you want a raw approach against the image file, then use a 
deduplication backup tool (block based backups).