Hi Greg,
I have just now added a single drive/osd to a clean cluster, and can
see the degradation immediately. We are on ceph 10.2.9 everywhere.
Here is how the cluster looked before the OSD got added:
cluster d7b33135-0940-4e48-8aa6-1d2026597c2f
health HEALTH_WARN
noout flag(s) set
monmap e31: 3 mons at
{cephmon00=10.128.128.100:6789/0,cephmon01=10.128.128.101:6789/0,cephmon02=10.128.128.102:6789/0}
election epoch 46092, quorum 0,1,2
cephmon00,cephmon01,cephmon02
fsmap e26638: 1/1/1 up {0=cephmon01=up:active}, 2
up:standby
osdmap e681227: 1270 osds: 1270 up, 1270 in
flags noout,sortbitwise,require_jewel_osds
pgmap v54583934: 42496 pgs, 6 pools, 1488 TB data, 437
Mobjects
4471 TB used, 3416 TB / 7887 TB avail
42491 active+clean
5 active+clean+scrubbing+deep
client io 2193 kB/s rd, 27240 kB/s wr, 85 op/s rd, 47 op/s
wr
And this is shortly after it was added (after all the peering was
done):
cluster d7b33135-0940-4e48-8aa6-1d2026597c2f
health HEALTH_WARN
141 pgs backfill_wait
117 pgs backfilling
20 pgs degraded
20 pgs recovery_wait
56 pgs stuck unclean
recovery 130/1376744346 objects degraded (0.000%)
recovery 3827502/1376744346 objects misplaced
(0.278%)
noout flag(s) set
monmap e31: 3 mons at
{cephmon00=10.128.128.100:6789/0,cephmon01=10.128.128.101:6789/0,cephmon02=10.128.128.102:6789/0}
election epoch 46092, quorum 0,1,2
cephmon00,cephmon01,cephmon02
fsmap e26638: 1/1/1 up {0=cephmon01=up:active}, 2
up:standby
osdmap e681238: 1271 osds: 1271 up, 1271 in; 258 remapped
pgs
flags noout,sortbitwise,require_jewel_osds
pgmap v54585141: 42496 pgs, 6 pools, 1488 TB data, 437
Mobjects
4471 TB used, 3423 TB / 7895 TB avail
130/1376744346 objects degraded (0.000%)
3827502/1376744346 objects misplaced (0.278%)
42210 active+clean
141 active+remapped+wait_backfill
117 active+remapped+backfilling
20 active+recovery_wait+degraded
7 active+clean+scrubbing+deep
1 active+clean+scrubbing
recovery io 17375 MB/s, 5069 objects/s
client io 12210 kB/s rd, 29887 kB/s wr, 4 op/s rd, 140 op/s
wr
Even though there was no failure, we have 20 degraded PGs, and 130
degraded objects. My expectation was for some data to move around,
start filling the added drive, but I would not expect to see
degraded objects or PGs.
Also, as time passes, the number of degraded objects increases
steadily, here is a snapshot a little later:
cluster d7b33135-0940-4e48-8aa6-1d2026597c2f
health HEALTH_WARN
63 pgs backfill_wait
4 pgs backfilling
67 pgs stuck unclean
recovery 706/1377244134 objects degraded (0.000%)
recovery 843267/1377244134 objects misplaced
(0.061%)
noout flag(s) set
monmap e31: 3 mons at
{cephmon00=10.128.128.100:6789/0,cephmon01=10.128.128.101:6789/0,cephmon02=10.128.128.102:6789/0}
election epoch 46092, quorum 0,1,2
cephmon00,cephmon01,cephmon02
fsmap e26640: 1/1/1 up {0=cephmon01=up:active}, 2
up:standby
osdmap e681569: 1271 osds: 1271 up, 1271 in; 67 remapped
pgs
flags noout,sortbitwise,require_jewel_osds
pgmap v54588554: 42496 pgs, 6 pools, 1488 TB data, 437
Mobjects
4471 TB used, 3423 TB / 7895 TB avail
706/1377244134 objects degraded (0.000%)
843267/1377244134 objects misplaced (0.061%)
42422 active+clean
63 active+remapped+wait_backfill
5 active+clean+scrubbing+deep
4 active+remapped+backfilling
2 active+clean+scrubbing
recovery io 779 MB/s, 229 objects/s
client io 306 MB/s rd, 344 MB/s wr, 138 op/s rd, 226 op/s wr
From past experience, the degraded object count keeps going up for
most of the time the disk is being filled. Towards the end it
decreases. Is writing to a pool that is waiting for backfilling
causing degraded objects to appear perhaps?
I took a 'pg dump' before and after the change, as well as an 'osd
tree' before and after. All these are available at
http://voms.simonsfoundation.org:50013/m1Maf76sV1kS95spXQpijycmne92yjm/ceph-20170720/
All pools are now with replicated size 3 and min size 2. Let me know
if any other info would be helpful.
Andras
On 07/06/2017 02:30 PM, Andras Pataki
wrote:
Hi Greg,
At the moment our cluster is all in balance. We have one failed
drive that will be replaced in a few days (the OSD has been
removed from ceph and will be re-added with the replacement
drive). I'll document the state of the PGs before the addition of
the drive and during the recovery process and report back.
We have a few pools, most are on 3 replicas now, some with
non-critical data that we have elsewhere are on 2. But I've seen
the degradation even on the 3 replica pools (I think in my
original example there was an example of such a pool as well).
Andras
On 06/30/2017 04:38 PM, Gregory
Farnum wrote:
On Wed, Jun 21, 2017 at 6:57 AM Andras Pataki
< apataki@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Hi cephers,
I noticed something I don't understand about ceph's
behavior when adding an OSD. When I start with a clean
cluster (all PG's active+clean) and add an OSD (via
ceph-deploy for example), the crush map gets updated and
PGs get reassigned to different OSDs, and the new OSD
starts getting filled with data. As the new OSD gets
filled, I start seeing PGs in degraded states. Here is
an example:
pgmap v52068792: 42496 pgs, 6
pools, 1305 TB data, 390 Mobjects
3164 TB used, 781 TB / 3946 TB
avail
8017/994261437 objects
degraded (0.001%)
2220581/994261437 objects
misplaced (0.223%)
42393 active+clean
91
active+remapped+wait_backfill
9
active+clean+scrubbing+deep
1
active+recovery_wait+degraded
1 active+clean+scrubbing
1
active+remapped+backfilling
Any ideas why there would be any persistent degradation
in the cluster while the newly added drive is being
filled? It takes perhaps a day or two to fill the drive
- and during all this time the cluster seems to be
running degraded. As data is written to the cluster,
the number of degraded objects increases over time.
Once the newly added OSD is filled, the cluster comes
back to clean again.
Here is the PG that is degraded in this picture:
7.87c 1 0 2 0 0 4194304 7 7
active+recovery_wait+degraded 2017-06-20
14:12:44.119921 344610'7 583572:2797
[402,521] 402 [402,521] 402 344610'7
2017-06-16 06:04:55.822503 344610'7 2017-06-16
06:04:55.822503
The newly added osd here is 521. Before it got added,
this PG had two replicas clean, but one got forgotten
somehow?
This sounds a bit concerning at first glance. Can you
provide some output of exactly what commands you're
invoking, and the "ceph -s" output as it changes in
response?
I really don't see how adding a new OSD can result in
it "forgetting" about existing valid copies — it's
definitely not supposed to — so I wonder if there's a
collision in how it's deciding to remove old locations.
Are you running with only two copies of your data? It
shouldn't matter but there could also be errors resulting
in a behavioral difference between two and three copies.
-Greg
Other remapped PGs have 521 in their "up" set but still
have the two existing copies in their "acting" set - and
no degradation is shown. Examples:
2.f24 14282 0 16 28564 0
51014850801 3102 3102
active+remapped+wait_backfill 2017-06-20
14:12:42.650308 583553'2033479 583573:2033266
[467,521] 467 [467,499] 467
582430'2033337 2017-06-16 09:08:51.055131
582036'2030837 2017-05-31 20:37:54.831178
6.2b7d 10499 0 140 20998 0
37242874687 3673 3673
active+remapped+wait_backfill 2017-06-20
14:12:42.070019 583569'165163 583572:342128
[541,37,521] 541 [541,37,532] 541
582430'161890 2017-06-18 09:42:49.148402
582430'161890 2017-06-18 09:42:49.148402
We are running the latest Jewel patch level everywhere
(10.2.7). Any insights would be appreciated.
Andras
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