[linux-lvm] ANNOUNCE: an experimental implementation of snapshot merging

[Brian J. Murrell]

On Tue, 2008-06-03 at 15:43 -0500, Chris Cox wrote:
> 
> I would think this would be VERY hard to do since both the "origin" and
> "snapshot" change (file deletes, etc).

I don't think it's as difficult as you are thinking it is.  You are
thinking of synchronizing filesystems, at the filesystem level, but
merging a snapshot back up into the origin does not deal with files or
even filesystems.  It deals with block devices and blocks, and is really
nothing more than a coordinated:

for each COW_block in snapshot; do
    for other_snapshot of origin; do
        copy origin[COW_block] to other_snapshot[COW_block]
        copy snapshot[COW_block] to origin[COW_block]
    done
done

> Do you have a set of rules you
> use for the merge?

There is no filesystem level merge.  There are no rules needed.

b.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 189 bytes
Desc: This is a digitally signed message part
URL: <http://listman.redhat.com/archives/linux-lvm/attachments/20080603/6ed73055/attachment.sig>