Gavin McCullagh wrote:
> Hi,
>
> up until now, we've tended to keep backups in a fairly ad hoc manner.
> People looking after a particular system have worked out their own way, be
> it a proprietary backup tool, or a script of some sort. We've started
> setting up bacula and I hope we'll be in a position to backup nearly every
> system with it, which will have substantial advantages.
>
> For several of the larger systems, the script used is a standard enough
> combination of rsync and hard links. It's based on ideas used here:
>
> http://www.mikerubel.org/computers/rsync_snapshots/
>
> As there is no one "full backup", you don't need to keep several full
> backups, you basically just delete the tree of old backups you don't need.
> A number of our servers tend to gradually accumulate files, most of which
> then go unchanged (eg maildirs, video libraries, ...) so this backup method
> tends to be very space efficient.
>
> One server has about 300GB of data. We keep 31 consecutive days and the 1st
> of each month prior to that. This costs us about 450GB of disk space.
>
> I'm now looking at setting up bacula for this backup -- initially using
> disk storage. As a starting point, looking at chapter 25 of the manual, it
> would cost about (300GB*6)*(compression ratio) just for the full backups
> which is a little rough and probably involves a very large amount of
> redundancy. While SATA disks are pretty cheap, caddies for our Dell MD1000
> disk array aren't :-(
>
> To try and reduce the space requirements, I'm considering more spread out
> schemes such as:
>
> - full backups on first sunday of the quarter to fullvol-[123]
> -> recycled after 6 months
> - differential backups on first sunday of the (other) months to
> diffvol-[1234]
> -> recycled after 3 months
> - incremental backups every other day to incvol-1
> -> recycled at end of each month
>
> which I think should cost us more like (300GB*3+diffs+incs)*(comp_ratio).
>
> Are there pitfalls in spreading things out this far? We may move to tape
> at some point (either spooling or migrate), but I don't have a budget to
> buy LTO4 tape drives at the minute. Is there some other technique I'm
> missing that would more efficiently store these larger data stores?
>
The first thing I notice is that you're doing incremental backups every
other day. I'd really encourage you to do them everyday if you can,
otherwise on that odd day you're going to be really unhappy when a disk
crashes and you've lots 2 days worth of data rather than just 1.
As far as spreading out the full and differential backups, the only
downside that I can see is that it'll increase your restore time as
you'll need to go back to a differential and a full to do a restore and
a lot can change in there.
One question to think about is how far back do you need to be able to
restore? I'm finding that a lot of places only need to go back 60 to 90
days. If that's the case, then you set your recycle time much lower on
your full backups and you only keep 1 or 2 full backups.
--
Jon Schewe | http://mtu.net/~jpschewe
If you see an attachment named signature.asc, this is my digital
signature. See http://www.gnupg.org for more information.
For I am convinced that neither death nor life, neither angels nor
demons, neither the present nor the future, nor any powers,
neither height nor depth, nor anything else in all creation, will
be able to separate us from the love of God that is in Christ
Jesus our Lord. - Romans 8:38-39
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