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.d...@externos.ciemat.es
<mailto:miguelangel.d...@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/
CETA-Ciemat logo <http://www.ceta-ciemat.es/>
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