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[FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>]

Thanks for the explanation!

On Mon, 2 May 2011 21:12:22 -0700
Michael Barton <mike-launchpad@xxxxxxxxxxxxxxxx> wrote:

> What I've been playing with is having a manifest that contains hashes
> of (4mb) chunks for the volume's backups.  When a user initiates a new
> backup, dm-snapshot does its thing and gives me a block device.  I
> read and hash chunks from that block device and compare them to the
> manifest, uploading any that differ to Swift, then update the manifest
> with the new backup.

Ah, you read and hash chunks from the "whole" block device. I
misunderstood the point.

> The restore uses fuse with some basic bitmap logic to lazy load chunks
> from Swift on demand, plus a background thread that fills them in
> autonomously.  I've been pretty happy with fuse's performance and
> stability (python-fuse that is; fusepy is really slow).

You create a loopback device of the fuse file and set up a dm-snap
device by using it, right?

Tomo