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From: Joel Becker <Joel.Becker@oracle.com>
Subject: Re: [PATCH 1/3] fs: Document the reflink(2) system
	call.
Date: Tue, 5 May 2009 15:39:16 -0700
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Cc: Theodore Tso <tytso@mit.edu>, Jamie Lokier <jamie@shareable.org>,
        linux-fsdevel@vger.kernel.org, Chris Mason <chris.mason@oracle.com>,
        jim owens <jowens@hp.com>, "Daniel P. Berrange" <berrange@redhat.com>,
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To: James Morris <jmorris@namei.org>
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On Wed, May 06, 2009 at 08:32:07AM +1000, James Morris wrote:
> On Tue, 5 May 2009, Joel Becker wrote:
> 
> > 	And if your file is actually a disk image, you get snapping of
> > disks for free :-)
> 
> Indeed... I think a great use-case scenario for this will be snapshotting 
> VM images, as well as fast and space-efficient instantiation of VMs.

	I did the initial design work (ocfs2's refcount tree structure)
to support snapping VM images.  I came up with the reflink() interface
when I realized the structure would back space-efficient instantiation,
or "shallow clones".  Since then, we've been coming up with more and
more fun tricks that the generic reflink() interface allows us to do.

Joel

-- 

"For every complex problem there exists a solution that is brief,
     concise, and totally wrong."
                                        -Unknown

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127