The default rules are sane for small clusters with few failure domains. Anything larger than a single rack should customize their rules. It's a good idea to figure this out early. Changes to your CRUSH rules can result in a large percentage of data moving around, which will make your cluster unusable until the migration completes. It is possible to make changes after the cluster has a lot of data. From what I've been able to figure out, it involves a lot of work to manually migrate data to new pools using the new rules. On Thu, Aug 21, 2014 at 6:23 AM, Sean Noonan <Sean.Noonan at twosigma.com> wrote: > Ceph uses CRUSH (http://ceph.com/docs/master/rados/operations/crush-map/) > to determine object placement. The default generated crush maps are sane, > in that they will put replicas in placement groups into separate failure > domains. You do not need to worry about this simple failure case, but you > should consider the network and disk i/o consequences of re-replicating > large amounts of data. > > Sean > ________________________________________ > From: ceph-users [ceph-users-bounces at lists.ceph.com] on behalf of > LaBarre, James (CTR) A6IT [James.LaBarre at Cigna.com] > Sent: Thursday, August 21, 2014 9:17 AM > To: ceph-users at ceph.com > Subject: [ceph-users] Question on OSD node failure recovery > > I understand the concept with Ceph being able to recover from the failure > of an OSD (presumably with a single OSD being on a single disk), but I?m > wondering what the scenario is if an OSD server node containing multiple > disks should fail. Presuming you have a server containing 8-10 disks, your > duplicated placement groups could end up on the same system. From diagrams > I?ve seen they show duplicates going to separate nodes, but is this in fact > how it handles it? > > > ------------------------------------------------------------------------------ > CONFIDENTIALITY NOTICE: If you have received this email in error, > please immediately notify the sender by e-mail at the address shown. > This email transmission may contain confidential information. This > information is intended only for the use of the individual(s) or entity to > whom it is intended even if addressed incorrectly. Please delete it from > your files if you are not the intended recipient. Thank you for your > compliance. Copyright (c) 2014 Cigna > > ============================================================================== > _______________________________________________ > ceph-users mailing list > ceph-users at lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.ceph.com/pipermail/ceph-users-ceph.com/attachments/20140821/c8226f44/attachment.htm>
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