----- Original Message -----
> From: "Deepak C Shetty" <deepa...@linux.vnet.ibm.com>
> To: vdsm-devel@lists.fedorahosted.org
> Sent: Wednesday, July 17, 2013 12:08:03 PM
> Subject: Re: [vdsm] Exploiting domain specific offload features
> On 07/17/2013 12:48 PM, M. Mohan Kumar wrote:
> > Hello,
> >
> > We are adding features such as server offloaded cloning, snapshot of
> > the files(ie VM disks) and zeroed vm disk allocation in GlusterFS. As of
> > now only BD xlator supports offloaded cloning & snapshot. Server
> > offloaded zeroing of VM disks is supported both by posix and BD xlator.
> > The initial approach is to use xattr interface to trigger this offload
> > features such as
> > # setfattr -n "clone" -v "path-to-new-clone-file" path-to-source-file
> > will create clone of path-to-source-file in path-to-new-clone-file.
> > Cloning is done in GlusterFS server side and its kind of server
> > offloaded copy. Similarly snapshot can also be taken using setfattr
> > approach.
> >
> > GlusterFS storage domain is already part of VDSM and we want to exploit
> > offload features provided by GlusterFS through VDSM. Is there any way to
> > exploit these features from VDSM as of now?
> Mohan,
>      IIUC, zeroing of files in GlusterFS is supported for both posix and
> block backends of GlusterFS
> Today VDSM does zeroing (as part of preallocated vmdisk flow) itself
> using 'dd'. If GlusterFS supports
> zeroing.... this feature can be exploited in VDSM (by overriding create
> volume flow as needed) so that we can save
> compute resources on the VDSM host, when Gluster domain is being used.
>      Regarding exploiting clone and snapshot, IIUC these are very native
> to VDSM today... it expects that snapshots are qcow2 based and they form
> the image chain etc... With snapshot and clone handled in Gluster
> transparently, these
> notions of VDSM will be broken, so it probably needs a lot of changes in
> lots of places in VDSM to exploit these.
> Federico/Ayal,
>      Wanted to know your comments/opinion on this ?
> Is there a way to exploit these features in VDSM Gluster storage domain
> in an elegant way ?

I think we can already start exploiting cloning whenever we need to copy
a volume maintaining the same format (raw=>raw, cow=>cow).

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