On Tue, Jun 11, 2013 at 3:04 PM, Bryan Stillwell <bstillwell@xxxxxxxxxxxxxxx> wrote: > On Tue, Jun 11, 2013 at 3:50 PM, Gregory Farnum <greg@xxxxxxxxxxx> wrote: >> You should not run more than one active MDS (less stable than a >> single-MDS configuration, bla bla bla), but you can run multiple >> daemons and let the extras serve as a backup in case of failure. The >> process for moving an MDS is pretty easy: turn on a daemon somewhere >> else, confirm it's connected to the cluster, then turn off the old >> one. >> Doing it that way will induce ~30 seconds of MDS inavailability while >> it times out, but on cuttlefish you should be able to force an instant >> takeover if the new daemon uses the same name as the old one (I >> haven't worked with this much myself so I might be missing a detail; >> if this is important you should check). >> >> (These relatively simple takeovers are thanks to the MDS only storing >> data in RADOS, and are one of the big design considerations in the >> system architecture). > > Thanks Greg! > > That sounds pretty easy. Although it has me wondering what config > option differentiates between an active MDS and a backup MDS daemon? > > Bryan You can manipulate this with the "mds standby for name", "mds standby for rank", and "mds standby replay" config options — but in general it's just a race to see who contacts the monitor first. :) -Greg Software Engineer #42 @ http://inktank.com | http://ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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