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Date:      Wed, 16 May 2007 22:15:05 +0200
From:      Peter Schuller <peter.schuller@infidyne.com>
To:        Paul Schmehl <pauls@utdallas.edu>
Cc:        FreeBSD Questions <freebsd-questions@freebsd.org>
Subject:   Re: Best remote backup method?
Message-ID:  <464B6649.2030105@infidyne.com>
In-Reply-To: <437646E3279CED649940FB48@utd59514.utdallas.edu>
References:  <437646E3279CED649940FB48@utd59514.utdallas.edu>

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> I'm presently backing up two servers in a remote location to a usb driv=
e
> located elsewhere by using rsync over ssh (all three are FreeBSD boxes.=
)
> After the recent discussion about dump, I'm wondering if I would gain
> anything by using dump rather than rsync.  Has anyone used both?  Any
> thoughts as to which is "better" and why?
>=20
> The rsync command I use is:
> rsync -avz ${LOCALDIR} -e "ssh -i ${KEY}" ${REMOTEHOST}:${REMOTEDIR}

Personally I never find dump/restore practical since I seldom want to
backup entire filesystems for performance/diskspace reasons.

I have not found any truly perfect solution; what I am using most often
is rdiff-backup which combines the properties of incremental backups and
rsync. It keeps an up-to-date mirror along with reverse diffs.

The good parts are that:

* It works without hassle right off the bat over ssh. No fuss.

* It is able to backup ownership information without running as root,
because meta-data is stored separately from the files (but at the same
time the up-to-date mirror is a plain tree on disk so you do not
actually have to use rdiff-backup for restores unless you care about
ownership and such).

* Other than using the rsync algorithm for transfers, the actual reverse
diffs are also expressed at a more granular level than entire files. End
result is that a daily backup of that 5 gig log file will not consume 5
gigs of storage per day (but will be very slow to backup).

The main downsides are IMO:

* It's fairly slow. I don't generally see it saturating neither disk nor
networking. Sometimes it's CPU bound, but oftentimes it's just slow
without an obvious bottleneck (probably architectural in the protocol).

* It has some reliability issues. A common problem is that certain
meta-dat is kept in gzip files, and in certain cases of rdiff-backup
being interrupted these files will get corrupted and rdiff-backup will
refuse to function due to the gzip library throwing an exception.

* While it basically works like rsync with history and is thus very
simple to get started with, it does just that. If you want things like
automatic rotation schemes with hourly/daily/etc you have to script that
on top.


--=20
/ Peter Schuller

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