On Tue, 22 Nov 2016, Dan Van Der Ster wrote: > > On 22 Nov 2016, at 16:17, Sage Weil <sage@xxxxxxxxxxxx> wrote: > > > > On Tue, 22 Nov 2016, Dan Van Der Ster wrote: > >> Hi, > >> > >> I have a couple questions about http://tracker.ceph.com/issues/15653 > >> > >> In the ticket Sage discusses small/big drives, and the small drives get > >> more data than expected. > >> > >> But we observe this at the rack level: our cluster has four racks, with > >> 7, 8, 8, 4 hosts respectively. The rack with 4 hosts is ~35% more full > >> than the others. > >> > >> So AFAICT, because of #15653, CRUSH does not currently work well if you > >> try to build a pool which is replicated rack/host-wise when your > >> rack/hosts are not all ~identical in size. > > > > Right--it's not about devices, but items within a CRUSH bucket. > > Unfortunately we don't have a good technical solution for this yet. The > > best proposal so far is Adam's PR at > > > > https://github.com/ceph/ceph/pull/10218 > > > > but it leaves much to be desired. I think we can do better, hopefully in > > time for lumninous. > > > > In the meantime, you can underweight (devices in) small racks. :( > > Thanks Sage. So you confirm that reweighting alone won't solve this? Er... reweight will "solve" it in the sense that if you compensate with lower weights it'll avoid overfilling those OSDs... is that what you mean? s _______________________________________________ Ceph-large mailing list Ceph-large@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-large-ceph.com
