Le lundi 04 mars 2013 à 09:02 -0800, Gregory Farnum a écrit : > On Mon, Mar 4, 2013 at 12:19 AM, Olivier Bonvalet <ceph.list@xxxxxxxxx> wrote: > > Hello, > > > > I have a running cluster, which use the (previous) default CRUSH rule, > > with : > > step take default > > step choose firstn 0 type osd > > step emit > > > > Since I have multiple OSD in the same host, I need to change that to > > have better redondancy. > > My crush map use types datacenter → room → network → rack → host → osd. > > > > For now I would like to replicate per "network", I suppose I can simply > > replace "step choose firstn 0 type osd" per "step choose firstn 0 type > > network" ; but is it safe to do that on a running cluster ? > > Not quite — you'll want to do "step chooseleaf firstn 0 type network". > See http://ceph.com/docs/master/rados/operations/crush-map for details > on this stuff. > Yes, it is safe to do on a running cluster. > > > > And I suppose it will throw a lot of data move, is it possible to do > > that «slowly», to avoid production slowdown ? > > Yeah, it's likely to move the entire contents. If you're on Argonaut > you're kind of stuck; if Bobtail then you have some control through > the "osd_max_backfills" option (defaults to 10) that specifies how > many moves each OSD will let itself be involved in at once. You should > practice on a non-production cluster first to make sure you don't run > into issues with pgtemp or OSDMap generation, though. > -Greg > Thanks for your answer. So I made some tests on a dedicated spool, I was able to move data from «platter» to «SSD» very well, it's great. But I can't obtain that per "network" neither per "host" setup : with 2 hosts, each one with 2 OSD, and with a pool with use only 1 replica (so, 2 copies), I tried this rule : rule rbdperhost { ruleset 5 type replicated min_size 1 max_size 10 step take default step chooseleaf firstn 0 type host step emit } As a result I obtain some PG which stuck in «active+remapped» state. When querying one of this PG, I see that CRUSH find only one OSD up for this one and can't find an other OSD to set replica. If I well understand, in this case the "chooseleaf firstn 0 type host" say to Ceph to choose 2 differents hosts, then in each of them choose one OSD. So with 2 hosts, it should works, no ? Thanks, Olivier B. _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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