On Mon, Feb 22, 2016 at 9:29 AM, George Mihaiescu <lmihaiescu@xxxxxxxxx> wrote: > Hi, > > We have a fairly large Ceph cluster (3.2 PB) that we want to expand and we > would like to get your input on this. > > The current cluster has around 700 OSDs (4 TB and 6 TB) in three racks with > the largest pool being rgw and using a replica 3. > For non-technical reasons (budgetary, etc) we are considering getting three > more racks, but initially adding only two storage nodes with 36 x 8 TB > drives in each, which will basically cause the rack weights to be imbalanced > (three racks with weight around a 1000 and 288 OSDs, and three racks with > weight around 500 but only 72 OSDs) > > The one replica per rack CRUSH rule will cause existing data to be > re-balanced among all six racks, with OSDs in the new racks getting only a > proportionate amount of replicas. > > Do you see any possible problems with this approach? Should Ceph be able to > properly rebalance the existing data among racks with imbalanced weights? > > Thank you for your input and please let me know if you need additional info. This should be okay; you have multiple racks in each size and aren't trying to replicate a full copy to each rack individually. You can test it ahead of time with the crush tool, though: http://docs.ceph.com/docs/master/man/8/crushtool/ It may turn out you're using old tunables and want to update them first or something. -Greg _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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