Re: cross-subvolume cp --reflink

["Norbert Scheibner" <scno@gmx.net>]

> On: Sun, 01 Apr 2012 20:19:24 +0300 Konstantinos Skarlatos wrote

> > I use btrfs for my backups. Ones a day I rsync --delete --inplace the
> complete system to a subvolume, snapshot it, delete some tempfiles in the
> snapshot.
> 
> In my setup I rsync --inplace many servers and workstations, 4-6 times 
> a day into a 12TB btrfs volume, each one in its own subvolume. After 
> every backup a new ro snapshot is created.
> 
> I have many cross-subvolume duplicate files (OS files, programs, many 
> huge media files that are copied locally from the servers to the 
> workstations etc), so a good "dedupe" script could save lots of space, 
> and allow me to keep snapshots for much longer.

So the script should be optimized not to try to deduplicate the whole fs everytime but the newly written ones. You could take such a file list out of the rsync output or the btrfs subvolume find-new command.

Albeit the reflink patch, You could use such a bash-script inside one subvolume, after the rsync and before the snapshot. I don't know how much space it saves for You in this situation, but it's worth a try and a good way to develop such a script, because before You write anything to disc You can see how many duplicates are there and how much space could be freed.

MfG
    Norbert