On 07/07/17 14:03, David Turner wrote: > > So many of your questions depends on what your cluster is used for. We > don't even know rbd or cephfs from what you said and that still isn't > enough to fully answer your questions. I have a much smaller 3 node > cluster using Erasure coding for rbds as well as cephfs and it is fine > speed-wise for my needs with the cache tier on the hdds. Luminous will > remove the need for a cache tier to use Erasure coding if you can wait. > > Is your current cluster fast enough for your needs? Is Erasure coding > just for additional space? If so, moving to Erasure coding requires > you to copy your data from the replicated pool to the EC pool land you > will have 2 copies of your data until you feel confident enough to > delete the replicated copy. Elaborate on what you mean when you ask > how robust EC is, you then referred to replicated as simple. Are you > concerned it will add complexity or that it will be lacking features > of a replicated pool? > You can even use your usual osds (HDDs and SSD journals?) as a cache tier. I plan to do that for some low performance cold storage (where bandwidth is small importance, and iops is not at all). It only has to be replicated, and the rest depends on the performance you need. And with only 3 hosts, EC won't save you as much space or be as fault tolerant. With failure domain host, you might end up with k=2,m=1 and then have poor redundnacy and not much space saved. And with failure domain osd, you could save more space by increasing k, but even if you increase m, you might end up with both copies on the same node, making it not very fault tolerant. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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