[Openstack-operators] Shared storage for live-migration with NFS, Ceph and Lustre

Miguel A Diaz Corchero miguelangel.diaz at externos.ciemat.es
Tue Jun 23 07:27:22 UTC 2015

Hi Dmitry

After reading CephRDB the impressions were extremely good and even 
better than CephFS to ephemeral storage. Are you using qcow2 or raw 
type? I prefer qcow2, but in this case we cannot enable the writing 
cache in the cluster reducing a bit the performance. I should test the 
CephRDB performance of both (qcow2 and raw) before migrating to production.

Thanks for sharing your experience.

El 20/06/15 22:49, Dmitry Borodaenko escribió:
> 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 
> <mailto: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/
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