Den mån 26 nov. 2018 kl 09:39 skrev Stefan Kooman <stefan@xxxxxx>: > > It is a slight mistake in reporting it in the same way as an error, > > even if it looks to the > > cluster just as if it was in error and needs fixing. This gives the > > new ceph admins a > > sense of urgency or danger whereas it should be perfectly normal to add space to > > a cluster. Also, it could have chosen to add a fourth PG in a repl=3 > > PG and fill from > > the one going out into the new empty PG and somehow keep itself with 3 working > > replicas, but ceph chooses to first discard one replica, then backfill > > into the empty > > one, leading to this kind of "error" report. > > Thanks for the explanation. I agree with you that it would be more safe to > first backfill to the new PG instead of just assuming the new OSD will > be fine and discarding a perfectly healthy PG. We do have max_size 3 in > the CRUSH ruleset ... I wonder if Ceph would behave differently if we > would have max_size 4 ... to actually allow a fourth copy in the first > place ... I don't think the replication number is important, it's more of a choice which PERHAPS is meant to allow you to move PGs to a new drive when the cluster is near full, since it will clear out space lots faster if you just kill off one unneeded replica and starts writing to a new drive, whereas keeping all old replicas until data is 100% ok on the new replica will make new space not appear until a large amount of data has moved, which for large drives and large PGs might take a very long time. -- May the most significant bit of your life be positive. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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