Il 2021-03-31 14:41 Nicolas Kovacs ha scritto:
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 ?
Niki
Hi Nicolas,
the simpler approach would be to use a filesystem which natively
supports send/recv on another host.
You can be tempted to use btrfs, but having tested it I strongly advice
against it: it will horribly fragments and performance will be bad even
if disabling CoW (which, by the way, is automatically re-enabled by
snapshots).
I currently just use ZFS on Linux and it works very well. However, using
it in CentOS is not trouble-free and it has its own CLI and specific
issues to be aware; so, I understand if you don't want to go down this
rabbit hole.
The next best thing I can suggest is to use lvmthin and XFS, with
efficient block-level copies done to another host via tools as bdsync
[1] or blocksync [2] (of which I forked an advanced version). On the
receiving host, you should (again) use lvmthin and XFS with periodic
snapshots.
Finally, I would leave the current rsnapshot backups in-place: you will
simply copy from a virtual machine rather than from a bare metal host. I
found rsnapshot really useful and reliable, so I suggest to continue
using it even if efficient block-level backup are taken.
Just my 2 cents.
Regards.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx
GPG public key ID: FF5F32A8
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