Le 20/11/2018 à 18:39, Craig Barratt via BackupPC-users a écrit :
> Steve,
>
> You are exactly right - BackupPC's storage granularity is whole
> files. So, in the worst case, a single byte change to a file that is
> a unique will result in a new file in the pool. Rsync will only
> transfer the deltas, but the full file gets rebuilt on the server.
>
> Before I did the 4.x rewrite, I did some benchmarking on block-level
> or more granular deltas, but the typical performance improvement was
> modest and the effort to implement it was large. However, there are
> two cases where block-level or byte-level deltas would be very helpful
> - database files (as you mentioned) and VM images.
>
> Perhaps you could use $Conf{DumpPreUserCmd} to run a script that
> generates byte-level deltas, and exclude the original database files?
> You could have a weekly schedule where you copy the full database file
> on, eg, Sunday, and generate deltas every other day of the week. Then
> BackupPC will backup the full file once, and also grab each of the
> deltas. That way you'll have a complete database file once per week,
> and all the daily (cumulative) deltas.
That's what I do for VM images for the past 10 years now: I use chunkfs
[1] to expose big VM images (or block devices) as a set of fixed sized
chunks, which BackupPC can archive. This way I have only the delta to
transfert store. With BackupPC v4 I use a 2MB chunk size.
To restore, I just have to assemble the chunks back (I stack backuppcfs
and unchunkfs so there's no temp file anywhere). It's rock solid,
efficient, and performant. Already restored several TB of VM using this :-)
The same can be done for DB dumps.
[1] http://chunkfs.florz.de/
--
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*Daniel Berteaud*
FIREWALL-SERVICES SAS.
Société de Services en Logiciels Libres
Tel : 05 56 64 15 32
Matrix: @dani:fws.fr
/www.firewall-services.com/
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