On Wednesday, October 12, 2016, Emilien Macchi <emil...@redhat.com> wrote:

> On Wed, Oct 12, 2016 at 7:10 AM, Giulio Fidente <gfide...@redhat.com
> <javascript:;>> wrote:
> > hi,
> >
> > we introduced support for the deployment of Ceph in the liberty release
> so
> > that it could optionally be used as backend for one or more of Cinder,
> > Glance, Nova and more recently Gnocchi.
> >
> > We used to deploy Ceph MONs on the controller nodes and Ceph OSDs on
> > dedicated ceph-storage nodes so a deployment of OpenStack with Ceph would
> > need at least 1 more additional node to host a Ceph OSD.
> >
> > In our HA scenario the storage backends are configured as follows:
> >
> > Glance -> Swift
> > Nova (ephemeral) -> Local
> > Cinder (persistent) -> LVM (on controllers)
> > Gnocchi -> Swift
> >
> > The downside of the above configuration is that Cinder volumes can not be
> > replicated across the controller nodes and become unavailable if a
> > controller fails, while production environments generally expect
> persistent
> > storage to be highly available. Cinder volumes instead could even get
> lost
> > completely in case of a permanent failure of a controller.
> >
> > With the Newton release and the composable roles we can now deploy Ceph
> OSDs
> > on the compute nodes, removing the requirement we had for an additional
> node
> > to host a Ceph OSD.
> >
> > I would like to ask for some feedback on the possibility of deploying
> Ceph
> > by default in the HA scenario and use it as backend for Cinder.
> >
> > Also using Swift as backend for Glance and Gnocchi is enough to cover the
> > availability issue for the data, but it also means we're storing that
> data
> > on the controller nodes which might or might not be wanted; I don't see a
> > strong reason for defaulting them to Ceph, but it might make more sense
> when
> > Ceph is available; feedback about this would be appreciated as well.
> >
> > Finally a shared backend (Ceph) for Nova would allow live migrations but
> > probably decrease performances for the guests in general; so I'd be
> against
> > defaulting Nova to Ceph. Feedback?
>
> +1 on making ceph default backend for nova/glance/cinder/gnocchi.
> I think this is the most common use-case we currently have in our
> deployments AFIK.


 + 1 from me. Ceph is the recommended backend for gnocchi and this will
help a lot with some recent performance issue we have seen.

- Prad



> Also, I'll continue to work on scenarios jobs (scenario002 and
> scenario003 without Ceph to cover other use cases).
>
> > --
> > Giulio Fidente
> > GPG KEY: 08D733BA
> >
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> --
> Emilien Macchi
>
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