Hi Peter, > When I check for circles I found that running the upmap balancer alone never seems to create > any kind of circle in the graph By a circle, do you mean something like this? pg 1.a: 1->2 (upmap to put a chunk on 2 instead of 1) pg 1.b: 2->3 pg 1.c: 3->1 If so, then it's not surprising that the upmap balancer wouldn't create this situation by itself, since there's no reason for this set of upmaps to exist purely for balance reasons. I don't think the balancer needs any explicit code to avoid the situation because of this. > Running pgremapper + balancer created circles with sometimes several dozen nodes. I would update the docs of the pgremapper > to warn about this fact and guide the users to use undo-upmap to slowly remove the upmaps create by cancel-backfill. This is again not surprising, since cancel-backfill will do whatever's necessary to undo a set of CRUSH changes (and some CRUSH changes regularly lead to movement cycles like this), and then using the upmap balancer will only make enough changes to achieve balance, not undo everything that's there. > It might be a nice addition to pgremapper to add an option to optimze the upmap table. What I'm still missing here is the value in this. Are there demonstrable problems presented by a large upmap exception table (e.g. performance or operational)? Josh _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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