Open Stack

With Ceph, you'll want to use RBD instead of CephFS, we had OpenStack live
migration working with Ceph RBD for about a year and a half now, here's a
PDF slide deck with some details:
https://drive.google.com/open?id=0BxYswyvIiAEZUEp4aWJPYVNjeU0

If you take CephFS and the bottlenecks associated with POSIX metadata
(which you don't need to manage your boot volumes which are just block
devices) out of the way, the need to partition your storage cluster
disappears, a single Ceph cluster can serve all 40 nodes.

It may be tempting to combine compute and storage on the same nodes, but
there's a gotcha associated with that. Ceph OSD processes may be fairly
CPU-heavy at high IOPS loads or when rebalancing data after an disk dies or
a node goes offline, you'd have to figure out a way to isolated their CPU
usage from that of your workloads. Which is why, for example, Fuel allows
you to combine ceph-osd and compute roles on the same node, but Fuel
documentation discourages you from doing so.


On Wed, Jun 17, 2015 at 2:11 AM Miguel A Diaz Corchero <
miguelangel.diaz at externos.ciemat.es> wrote:

>  Hi friends.
>
> I'm evaluating different DFS to increase our infrastructure from 10 nodes
> to 40 nodes approximately. One of the bottleneck is the shared storage
> installed to enable the live-migration.
> Well, the selected candidate are NFS, Ceph or Lustre (which is already
> installed for HPC purpose).
>
> Creating a brief planning and avoiding network connectivities:
>
> *a)* with NFS and Ceph, I think it is possible but dividing the whole
> infrastructure (40 nodes) in smaller clusters, for instance; 10 nodes with
> 1 storage each one. Obviously, the live-migration is only possible between
> nodes on the same cluster (or zone)
>
> *b) *with Lustre, my idea is to connect all the nodes (40 nodes) to the
> same lustre (MDS) and use all the concurrency advantages of the storage.
> In this case, the live migration could be possible among all the nodes.
>
> I would like to ask you for any idea, comment or experience. I think the
> most untested case is b), but has anyone tried to use Lustre in a similar
> scenario? Any comment in any case a) o b) are appreciated.
>
> Thanks
> Miguel.
>
>
> --
> *Miguel Angel Díaz Corchero*
> *System Administrator / Researcher*
> *c/ Sola nº 1; 10200 TRUJILLO, SPAIN*
> *Tel: +34 927 65 93 17 Fax: +34 927 32 32 37*
>
> [image: CETA-Ciemat logo] <http://www.ceta-ciemat.es/>
>
> *
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