On Mon, Aug 20, 2018 at 10:45 PM Stefan Priebe - Profihost AG <s.priebe@xxxxxxxxxxxx> wrote: > > > Am 20.08.2018 um 22:38 schrieb Dan van der Ster: > > On Mon, Aug 20, 2018 at 10:19 PM Stefan Priebe - Profihost AG > > <s.priebe@xxxxxxxxxxxx> wrote: > >> > >> > >> Am 20.08.2018 um 21:52 schrieb Sage Weil: > >>> On Mon, 20 Aug 2018, Stefan Priebe - Profihost AG wrote: > >>>> Hello, > >>>> > >>>> since loic seems to have left ceph development and his wunderful crush > >>>> optimization tool isn'T working anymore i'm trying to get a good > >>>> distribution with the ceph balancer. > >>>> > >>>> Sadly it does not work as good as i want. > >>>> > >>>> # ceph osd df | sort -k8 > >>>> > >>>> show 75 to 83% Usage which is 8% difference which is too much for me. > >>>> I'm optimization by bytes. > >>>> > >>>> # ceph balancer eval > >>>> current cluster score 0.005420 (lower is better) > >>>> > >>>> # ceph balancer eval $OPT_NAME > >>>> plan spriebe_2018-08-20_19:36 final score 0.005456 (lower is better) > >>>> > >>>> I'm unable to optimize further ;-( Is there any chance to optimize > >>>> further even in case of more rebelancing? > >>> > >>> The scoring that the balancer module is doing is currently a hybrid of pg > >>> count, bytes, and object count. Picking a single metric might help a bit > >>> (as those 3 things are not always perfectly aligned). > >> > >> Hi, > >> > >> ok i found a bug in the balancer code which seems to be present in all > >> releases. > >> > >> 861 best_ws = next_ws > >> 862 best_ow = next_ow > >> > >> > >> should be: > >> > >> 861 best_ws = copy.deepcopy(next_ws) > >> 862 best_ow = copy.deepcopy(next_ow) > >> > >> otherwise it does not use the best but the last. > > > > Interesting... does that change improve things? > > It fixes the following (mgr debug output): > 2018-08-20 22:33:46.078525 7f2fbc3b6700 0 mgr[balancer] Step result > score 0.001152 -> 0.001180, misplacing 0.000912 > 2018-08-20 22:33:46.078574 7f2fbc3b6700 0 mgr[balancer] Score got > worse, taking another step > 2018-08-20 22:33:46.078770 7f2fbc3b6700 0 mgr[balancer] Balancing root > default (pools ['cephstor2']) by bytes > 2018-08-20 22:33:46.156326 7f2fbc3b6700 0 mgr[balancer] Step result > score 0.001152 -> 0.001180, misplacing 0.000912 > 2018-08-20 22:33:46.156374 7f2fbc3b6700 0 mgr[balancer] Score got > worse, taking another step > 2018-08-20 22:33:46.156581 7f2fbc3b6700 0 mgr[balancer] Balancing root > default (pools ['cephstor2']) by bytes > 2018-08-20 22:33:46.233818 7f2fbc3b6700 0 mgr[balancer] Step result > score 0.001152 -> 0.001180, misplacing 0.000912 > 2018-08-20 22:33:46.233868 7f2fbc3b6700 0 mgr[balancer] Score got > worse, taking another step > 2018-08-20 22:33:46.234043 7f2fbc3b6700 0 mgr[balancer] Balancing root > default (pools ['cephstor2']) by bytes > 2018-08-20 22:33:46.313212 7f2fbc3b6700 0 mgr[balancer] Step result > score 0.001152 -> 0.001180, misplacing 0.000912 > 2018-08-20 22:33:46.313714 7f2fbc3b6700 0 mgr[balancer] Score got > worse, trying smaller step 0.000244 > 2018-08-20 22:33:46.313887 7f2fbc3b6700 0 mgr[balancer] Balancing root > default (pools ['cephstor2']) by bytes > 2018-08-20 22:33:46.391586 7f2fbc3b6700 0 mgr[balancer] Step result > score 0.001152 -> 0.001152, misplacing 0.001141 > 2018-08-20 22:33:46.393374 7f2fbc3b6700 0 mgr[balancer] Balancing root > default (pools ['cephstor2']) by bytes > 2018-08-20 22:33:46.473956 7f2fbc3b6700 0 mgr[balancer] Step result > score 0.001152 -> 0.001180, misplacing 0.000912 > 2018-08-20 22:33:46.474001 7f2fbc3b6700 0 mgr[balancer] Score got > worse, taking another step > 2018-08-20 22:33:46.474046 7f2fbc3b6700 0 mgr[balancer] Success, score > 0.001155 -> 0.001152 > > BUT: > # ceph balancer eval myplan > plan myplan final score 0.001180 (lower is better) > > So the final plan does NOT contain the expected optimization. The > deepcopy fixes it. > > After: > # ceph balancer eval myplan > plan myplan final score 0.001152 (lower is better) > OK that looks like a bug. Did you create a tracker or PR? -- Dan > > > > Also, if most of your data is in one pool you can try ceph balancer > > eval <pool-name> > > Already tried this doesn't help much. > > Greets, > Stefan > > > > -- dan > > > >> > >> I'm also using this one: > >> https://github.com/ceph/ceph/pull/20665/commits/c161a74ad6cf006cd9b33b40fd7705b67c170615 > >> > >> to optimize by bytes only. > >> > >> Greets, > >> Stefan
