<div dir="ltr"><div><div>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:<br><a href="https://drive.google.com/open?id=0BxYswyvIiAEZUEp4aWJPYVNjeU0">https://drive.google.com/open?id=0BxYswyvIiAEZUEp4aWJPYVNjeU0</a><br><br></div>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.<br><br></div>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.<br><div><div><div><div><div><div><br></div></div></div></div></div></div></div><br><div class="gmail_quote"><div dir="ltr">On Wed, Jun 17, 2015 at 2:11 AM Miguel A Diaz Corchero <<a href="mailto:miguelangel.diaz@externos.ciemat.es">miguelangel.diaz@externos.ciemat.es</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
Hi friends.<br>
<br>
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.<br>
Well, the selected candidate are NFS, Ceph or Lustre (which is
already installed for HPC purpose). <br>
<br>
Creating a brief planning and avoiding network connectivities:<br>
<br>
<b>a)</b> 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)<br>
<br>
<b>b) </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.<br>
<br>
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.<br>
<br>
Thanks<br>
Miguel.<br>
<br>
<br>
<div>-- <br>
<i><font size="2"><span style="color:#000000"><span style="font-family:Century Gothic,sans-serif,10">Miguel
Angel Díaz Corchero</span></span></font></i><font size="2"><br>
<i><b><span style="font-family:Century Gothic,sans-serif">System
Administrator / Researcher</span></b></i><br>
<i><span style="font-family:Century Gothic,sans-serif">c/ Sola
nº 1; 10200 TRUJILLO, SPAIN</span></i><br>
<i><span style="font-family:Century Gothic,sans-serif">Tel: +34
927 65 93 17 Fax: +34 927 32 32 37</span></i>
<p><span><a href="http://www.ceta-ciemat.es/" target="_blank"><img src="cid:part1.07090705.05060805@externos.ciemat.es" alt="CETA-Ciemat logo" height="76" width="383" border="0"></a></span></p>
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