Thanks everyone for the replies. Very informative. However, should I have expected writes to pause if I'd had min_size set to 1 instead of 2? And yes, I was under the false impression that my rdb devices was a single object. That explains what all those other things are on a test cluster where I only created a single object! -- Adam Carheden On 03/20/2017 08:24 PM, Wes Dillingham wrote: > This is because of the min_size specification. I would bet you have it > set at 2 (which is good). > > ceph osd pool get rbd min_size > > With 4 hosts, and a size of 3, removing 2 of the hosts (or 2 drives 1 > from each hosts) results in some of the objects only having 1 replica > min_size dictates that IO freezes for those objects until min_size is > achieved. http://docs.ceph.com/docs/jewel/rados/operations/pools/#set-the-number-of-object-replicas > > I cant tell if your under the impression that your RBD device is a > single object. It is not. It is chunked up into many objects and spread > throughout the cluster, as Kjeti mentioned earlier. > > On Mon, Mar 20, 2017 at 8:48 PM, Kjetil Jørgensen <kjetil@xxxxxxxxxxxx > <mailto:kjetil@xxxxxxxxxxxx>> wrote: > > Hi, > > rbd_id.vm-100-disk-1 is only a "meta object", IIRC, it's contents > will get you a "prefix", which then gets you on to > rbd_header.<prefix>, rbd_header.prefix contains block size, > striping, etc. The actual data bearing objects will be named > something like rbd_data.prefix.%-016x. > > Example - vm-100-disk-1 has the prefix 86ce2ae8944a, the first > <block size> of that image will be named rbd_data. > 86ce2ae8944a.000000000000, the second <block size> will be > 86ce2ae8944a.000000000001, and so on, chances are that one of these > objects are mapped to a pg which has both host3 and host4 among it's > replicas. > > An rbd image will end up scattered across most/all osds of the pool > it's in. > > Cheers, > -KJ > > On Fri, Mar 17, 2017 at 12:30 PM, Adam Carheden <carheden@xxxxxxxx > <mailto:carheden@xxxxxxxx>> wrote: > > I have a 4 node cluster shown by `ceph osd tree` below. Monitors are > running on hosts 1, 2 and 3. It has a single replicated pool of size > 3. I have a VM with its hard drive replicated to OSDs 11(host3), > 5(host1) and 3(host2). > > I can 'fail' any one host by disabling the SAN network interface and > the VM keeps running with a simple slowdown in I/O performance > just as > expected. However, if 'fail' both nodes 3 and 4, I/O hangs on > the VM. > (i.e. `df` never completes, etc.) The monitors on hosts 1 and 2 > still > have quorum, so that shouldn't be an issue. The placement group > still > has 2 of its 3 replicas online. > > Why does I/O hang even though host4 isn't running a monitor and > doesn't have anything to do with my VM's hard drive. > > > Size? > # ceph osd pool get rbd size > size: 3 > > Where's rbd_id.vm-100-disk-1? > # ceph osd getmap -o /tmp/map && osdmaptool --pool 0 > --test-map-object > rbd_id.vm-100-disk-1 /tmp/map > got osdmap epoch 1043 > osdmaptool: osdmap file '/tmp/map' > object 'rbd_id.vm-100-disk-1' -> 0.1ea -> [11,5,3] > > # ceph osd tree > ID WEIGHT TYPE NAME UP/DOWN REWEIGHT PRIMARY-AFFINITY > -1 8.06160 root default > -7 5.50308 room A > -3 1.88754 host host1 > 4 0.40369 osd.4 up 1.00000 1.00000 > 5 0.40369 osd.5 up 1.00000 1.00000 > 6 0.54008 osd.6 up 1.00000 1.00000 > 7 0.54008 osd.7 up 1.00000 1.00000 > -2 3.61554 host host2 > 0 0.90388 osd.0 up 1.00000 1.00000 > 1 0.90388 osd.1 up 1.00000 1.00000 > 2 0.90388 osd.2 up 1.00000 1.00000 > 3 0.90388 osd.3 up 1.00000 1.00000 > -6 2.55852 room B > -4 1.75114 host host3 > 8 0.40369 osd.8 up 1.00000 1.00000 > 9 0.40369 osd.9 up 1.00000 1.00000 > 10 0.40369 osd.10 up 1.00000 1.00000 > 11 0.54008 osd.11 up 1.00000 1.00000 > -5 0.80737 host host4 > 12 0.40369 osd.12 up 1.00000 1.00000 > 13 0.40369 osd.13 up 1.00000 1.00000 > > > -- > Adam Carheden > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com> > > > > > -- > Kjetil Joergensen <kjetil@xxxxxxxxxxxx <mailto:kjetil@xxxxxxxxxxxx>> > SRE, Medallia Inc > Phone: +1 (650) 739-6580 <tel:(650)%20739-6580> > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx <mailto:ceph-users@xxxxxxxxxxxxxx> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com> > > > > > -- > Respectfully, > > Wes Dillingham > wes_dillingham@xxxxxxxxxxx <mailto:wes_dillingham@xxxxxxxxxxx> > Research Computing | Infrastructure Engineer > Harvard University | 38 Oxford Street, Cambridge, Ma 02138 | Room 210 > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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