Re: [ANNOUNCE] Btrfs: a copy on write, snapshotting FS

[david]

On Tue, 19 Jun 2007, Chris Mason wrote:

> > > 3. De-de-duplicate blocks on disk, i.e. copy them on write
> > >
> > > I suppose that de-duplication itself would be done by some user space
> > > process that would scan files, determine blocks with the same data and
> > > then de-duplicate them by using syscall or IOCTL (2).
> > >
> > > That would be very usable feature, which in most cases would allow to
> > > shrink occupied disk space on 50-90%.
> >
> > Have you references for this number?
> > In my experience one gets a lot of benefit from
> > the much simpler process of "de-duplication" of files.
>
> Yes, I would expect simple hard links to be a better solution for this,
> but the feature request is not that out of line.  I actually had plans
> on implementing auto duplicate block reuse earlier in btrfs.

with COW de-duplication you can merge things that have vastly different 
permissions. hard-links can't be used if different people have write 
permission.

David Lang

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