[Dirvish] btrfs support: v3 / "cow" option v1

[Adrian von Bidder]

Wrong button ...

here it is. Against 1.2.1

On Friday 04 March 2011 22.24:46 Adrian von Bidder wrote:
> Heyho!
> 
> I had a few moments to spare recently...
> 
> Summary: support using btrfs snapshots instead of hardlinked rsync trees.
> Also uses the --inplace option to rsync, so for changed files only the
> modified parts will be duplicated. (Hmm. rsync doesn't use fallocate(2)
> to punch holes in files yet, I assume, so there's room for improvement
> here for cases where a piece of a file has been cut out, as in a video
> stream.)
> 
> Also: a (first?) batch of patches that support data deduplication has
> been posted to the btrfs mailing list in January, so btrfs will be even
> more interesting in the medium future for those who use dirvish to
> backup a number of similar machines to a central backup machine. Not
> sure when this will be really available though...
> 
> Change vs. the first versions: as was proposed in the original discussion
> of this, the "btrfs" option has now been renamed into "cow" (copy on
> write); supported values are 0 (default) and btrfs. Supporting other cow
> filesystems is left as an exercise to the reader.
> 
> Status: while this is running here, I've only just written this code a
> few days ago, so some testing / feedback is welcome.
> 
> Since I expect there are not that many users of this yet, no migration
> path for old vaults is provided, I didn't want to bloat the code with
> support code for stuff that wasn't even released. Just insert "cow:
> btrfs" into all summary files (and default.conf, of course) and you're
> fine.
> 
> cheers
> -- vbi

-- 
The Free Software Foundation: The gang that couldn't price-fix straight!
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