> If you set min_size 2 before taking the OSDs down, that does seem odd.
I think I don’t get the exact concept of min_size in the crush Crush ruleset. The documentation (http://docs.ceph.com/docs/master/rados/operations/crush-map/ <http://docs.ceph.com/docs/master/rados/operations/crush-map/>) states: min_size Description: If a pool makes fewer replicas than this number, CRUSH will NOT select this rule. Type: Integer Purpose: A component of the rule mask. Required: Yes Default: 1 Assuming that I want my scenario to work (5 OSDs, 2+3 EC Pool, 3 OSDs down, still reading my data), how do I have to configure my pool exactly to work? Or is this simply not possible at this point? I just want to be sure that I have no errors in my configuration. > Yeah, we just don't have a way of serving reads without serving writes at the > moment. It's a limit of the architecture. Thank you, this is good to know, particularly because I didn’t find anything about it on the documentation. - Jonas > Am 07.06.2017 um 21:40 schrieb Gregory Farnum <gfar...@redhat.com>: > > > > On Wed, Jun 7, 2017 at 12:30 PM Jonas Jaszkowic > <jonasjaszko...@googlemail.com <mailto:jonasjaszko...@googlemail.com>> wrote: > >> Am 07.06.2017 um 20:29 schrieb Gregory Farnum <gfar...@redhat.com >> <mailto:gfar...@redhat.com>>: >> >> We prevent PGs from going active (and serving writes or reads) when they >> have less than "min_size" OSDs participating. This is generally set so that >> we have enough redundancy to recover from at least one OSD failing. > > Do you mean the min_size value from the crush rule? I set min_size = 2, so a > 2+3 EC pool with 3 killed OSDs still has the minimum amount of 2 OSDs and > should be able > to fully recover data, right? > > If you set min_size 2 before taking the OSDs down, that does seem odd. > > >> In your case, you have 2 OSDs and the failure of either one of them results >> in the loss of all written data. So we don't let you go active as it's not >> safe. > > > I get that it makes no sense to serve writes at this point because we cannot > provide the desired redundancy, but how is preventing me from going active > more safe than just serving reads? I think what bugs me is that by definition > of the used erasure code, we should be able to loose 3 OSDs and still get our > data back - which is not the case in this scenario because our cluster > refuses to go active. > > Yeah, we just don't have a way of serving reads without serving writes at the > moment. It's a limit of the architecture. > > -Greg > PS: please keep this on the list. It spreads the information and archives it > for future reference by others. :) >
_______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
