On Mon, Mar 21, 2016 at 11:45 AM, Christian Sarrasin <c.nntp@xxxxxxxxxxxxxxxxxx> wrote: > Hi there, > > The docs have an ominous warning that one shouldn't run the RBD client (to > mount block devices) on a machine which also serves OSDs [1] > > Due to budget constraints, this topology would be useful in our situation. > Couple of q's: > > 1) Does the limitation also apply if the OSD daemon is run off a docker > container [2]? > > 2) Any similar restrictions for a machine running MON daemons? This is specifically a problem for kernel RBD clients, not userspace ones — the problem being that if you get into a low-memory situation, it may try to flush dirty pages out over RBD, which will make the OSD process try to allocate memory which may not be available. Deadlock! I don't think this should be a problem if you're running librbd in KVM etc, but I don't *think* Docker provides enough isolation to prevent it as a theoretical possibility. Monitors shouldn't be an issue, although if they go down you're going to have a very, very unhappy cluster so I wouldn't call it wise if there's any possibility of resource contention -Greg _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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