On Tue, Jul 23, 2013 at 8:54 AM, Matthew Walster <matthew@xxxxxxxxxxx> wrote: > I've got a relatively small Ceph cluster I'm playing with at the moment, and > against advice, I'm running the MONs on the OSDs. > > Ideally, I'd like to have half the OSDs in a different facility and > therefore have one MON in each facility. > > Which gives the problem of where to put that pesky third MON... > > Is there any likely performance hit if I was to put the third MON in a > totally different datacenter, potentially in a different city? I know OSDs > need to be able to complete a transaction across all nodes in a placement > group before finishing a write, but what about MONs? > > As I understand it, the MONs just describe the topology, so surely having > them 5ms away shouldn't be that big of a deal? > > Just wondered what people's thoughts were. 5 milliseconds of latency should not be a problem for the monitor workload. You'll want to be sure and direct all the monitor clients to the monitor in their local DC though[1] or you'll get a lot more bandwidth going across DCs than is necessary. -Greg Software Engineer #42 @ http://inktank.com | http://ceph.com [1]: You can't force them to stay connected to a specific monitor, unfortunately, but you can just provide the address of the local monitor and that'll be the one they start up their sessions with and keep talking to unless it has a problem. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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