Thanks Mike. I get your point. There are still a few things confusing me: 1) We expand Ceph cluster by adding more OSDs, which will trigger re-balance PGs across the old & new OSDs, and likely it will break the optimized PG numbers for the cluster. 2) We can add more PGs which will trigger re-balance objects across old & new PGs. So: 1) What is the recommended way to expand the cluster by adding OSDs (and potentially adding PGs), should we do them at the same time? 2) What is the recommended way to scale a cluster from like 1PB to 2PB, should we scale it to like 1.1PB to 1.2PB or move to 2PB directly? Thanks, Guang On Oct 10, 2013, at 11:10 AM, Michael Lowe wrote: > There used to be, can't find it right now. Something like 'ceph osd set pg_num <num>' then 'ceph osd set pgp_num <num>' to actually move your data into the new pg's. I successfully did it several months ago, when bobtail was current. > > Sent from my iPad > >> On Oct 9, 2013, at 10:30 PM, Guang <yguang11@xxxxxxxxx> wrote: >> >> Thanks Mike. >> >> Is there any documentation for that? >> >> Thanks, >> Guang >> >>> On Oct 9, 2013, at 9:58 PM, Mike Lowe wrote: >>> >>> You can add PGs, the process is called splitting. I don't think PG merging, the reduction in the number of PGs, is ready yet. >>> >>>> On Oct 8, 2013, at 11:58 PM, Guang <yguang11@xxxxxxxxx> wrote: >>>> >>>> Hi ceph-users, >>>> Ceph recommends the PGs number of a pool is (100 * OSDs) / Replicas, per my understanding, the number of PGs for a pool should be fixed even we scale out / in the cluster by adding / removing OSDs, does that mean if we double the OSD numbers, the PG number for a pool is not optimal any more and there is no chance to correct it? >>>> >>>> >>>> Thanks, >>>> Guang >>>> _______________________________________________ >>>> ceph-users mailing list >>>> ceph-users@xxxxxxxxxxxxxx >>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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