[Gluster-devel] reflink support for glusterfs and gluster-block using it for taking snapshots

[Pranith Kumar Karampuri]

On Thu, Nov 9, 2017 at 8:26 PM, Niels de Vos <ndevos at redhat.com> wrote:

> On Tue, Nov 07, 2017 at 05:59:32PM +0530, Pranith Kumar Karampuri wrote:
> > On Tue, Nov 7, 2017 at 5:16 PM, Niels de Vos <ndevos at redhat.com> wrote:
> >
> > > On Tue, Nov 07, 2017 at 07:43:17AM +0530, Pranith Kumar Karampuri
> wrote:
> > > > hi,
> > > >      I just created a github issue for reflink support
> > > > <https://github.com/gluster/glusterfs/issues/349>(#349) in
> glusterfs. We
> > > > are intending to use this feature to do block snapshots in
> gluster-block.
> > > >
> > > > Please let us know your comments on the github issue. I have added
> the
> > > > changes we may need for xlators I know a little bit about. Please
> help in
> > > > identifying gaps in implementing this FOP.
> > >
> > > For gluster-block it may be easier to have snapshot support in
> > > tcmu-runner instead? The qcow2 format would be ideal, and is in use by
> > > different Virtual Machine approaches running on Gluster already. There
> > > even is an upstream issue open for it:
> > >   https://github.com/open-iscsi/tcmu-runner/issues/32
> > >
> > > Contributing towards this might be quicker than implementing file
> > > snapshot support in Gluster?
> > >
> >
> > We tried that route by talking Fam Zheng, but the solution won't be
> > delivered in the timelines we are looking for.
> > So we went with this approach.
>
> Ok, I am not sure if adding support for reflink in Gluster has an
> immediate benefit. It surely would be a great feature to have, but I do
> not know if it will land in enterprise kernels soon.
>

https://github.com/gluster/glusterfs/issues/377 should address this concern
until reflink becomes mainstream.


>
> That said, I opened a GitHub issue to get reliable snapshot support in
> gluster-block. It describes an idea of the interface that could be
> implemented now already, without relying on reflink.
>
>   https://github.com/gluster/gluster-block/issues/42
>
> Obviously there is a need to sync/freeze data through tcmu-runner. This
> might require implementing a fsfreeze(8) like command in targetcli and
> tcmu-runner.
>
> Comments most welcome!
> Niels
>



-- 
Pranith
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