I've been struggling with this one for a few days now.  We had an OSD report as 
near full a few days ago.  Had this happen a couple of times before and a 
reweight-by-utilization has sorted it out in the past.  Tried the same again 
but this time we ended up with a couple of pgs in a state of backfill_toofull 
and a handful of misplaced objects as a result.

Tried doing the reweight a few more times and it's been moving data around.  We 
did have another osd trigger the near full alert but running the reweight a 
couple more times seems to have moved some of that data around a bit better.  
However, the original near_full osd doesn't seem to have changed much and the 
backfill_toofull pgs are still there.  I'd keep doing the 
reweight-by-utilization but I'm not sure if I'm heading down the right path and 
if it will eventually sort it out.

We have 14 pools, but the vast majority of data resides in just one of those 
pools (pool 20).  The pgs in the backfill state are in pool 2 (as far as I can 
tell).  That particular pool is used for some cephfs stuff and has a handful of 
large files in there (not sure if this is significant to the problem).

All up, our utilization is showing as 55.13% but some of our OSDs are showing 
as 76% in use with this one problem sitting at 85.02%.  Right now, I'm just not 
sure what the proper corrective action is.  The last couple of reweights I've 
run have been a bit more targetted in that I've set it to only function on two 
OSDs at a time.  If I run a test-reweight targetting only one osd, it does say 
it will reweight OSD 9 (the one at 85.02%).  I gather this will move data away 
from this OSD and potentially get it below the threshold.  However, at one 
point in the past couple of days, it's shown as no OSDs in a near full state, 
yet the two pgs in backfill_toofull didn't change.  So, that's why I'm not sure 
continually reweighting is going to solve this issue.

I'm a long way from knowledgable on Ceph so I'm not really sure what 
information is useful here.  Here's a bit of info on what I'm seeing.  Can 
provide anything else that might help.


Basically, we have a three node cluster but only two have OSDs.  The third is 
there simply to enable a quorum to be established.  The OSDs are evenly spread 
across these two needs and the configuration of each is identical.  We are 
running Jewel and are not in a position to upgrade at this stage.




# ceph --version
ceph version 10.2.11 (e4b061b47f07f583c92a050d9e84b1813a35671e)


# ceph health detail
HEALTH_WARN 2 pgs backfill_toofull; 2 pgs stuck unclean; recovery 33/62099566 
objects misplaced (0.000%); 1 near full osd(s)
pg 2.52 is stuck unclean for 201822.031280, current state 
active+remapped+backfill_toofull, last acting [17,3]
pg 2.18 is stuck unclean for 202114.617682, current state 
active+remapped+backfill_toofull, last acting [18,2]
pg 2.18 is active+remapped+backfill_toofull, acting [18,2]
pg 2.52 is active+remapped+backfill_toofull, acting [17,3]
recovery 33/62099566 objects misplaced (0.000%)
osd.9 is near full at 85%


# ceph osd df
ID WEIGHT  REWEIGHT SIZE   USE    AVAIL  %USE  VAR  PGS
 2 1.37790  1.00000  1410G   842G   496G 59.75 1.08  33
 3 1.37790  0.45013  1410G  1079G   259G 76.49 1.39  21
 4 1.37790  0.95001  1410G  1086G   253G 76.98 1.40  44
 5 1.37790  1.00000  1410G   617G   722G 43.74 0.79  43
 6 1.37790  0.65009  1410G   616G   722G 43.69 0.79  39
 7 1.37790  0.95001  1410G   495G   844G 35.10 0.64  40
 8 1.37790  1.00000  1410G   732G   606G 51.93 0.94  52
 9 1.37790  0.70007  1410G  1199G   139G 85.02 1.54  37
10 1.37790  1.00000  1410G   611G   727G 43.35 0.79  41
11 1.37790  0.75006  1410G   495G   843G 35.11 0.64  32
 0 1.37790  1.00000  1410G   731G   608G 51.82 0.94  43
12 1.37790  1.00000  1410G   851G   487G 60.36 1.09  44
13 1.37790  1.00000  1410G   378G   960G 26.82 0.49  38
14 1.37790  1.00000  1410G   969G   370G 68.68 1.25  37
15 1.37790  1.00000  1410G   724G   614G 51.35 0.93  35
16 1.37790  1.00000  1410G   491G   847G 34.84 0.63  43
17 1.37790  1.00000  1410G   862G   476G 61.16 1.11  50
18 1.37790  0.80005  1410G  1083G   255G 76.78 1.39  26
19 1.37790  0.65009  1410G   963G   375G 68.29 1.24  23
20 1.37790  1.00000  1410G   724G   614G 51.38 0.93  42
              TOTAL 28219G 15557G 11227G 55.13
MIN/MAX VAR: 0.49/1.54  STDDEV: 15.57


# ceph pg ls backfill_toofull
pg_stat objects mip degr misp unf bytes log disklog state state_stamp v 
reported up up_primary acting acting_primary last_scrub scrub_stamp 
last_deep_scrub deep_scrub_stamp
2.18 9 0 0 18 0 0 3653 3653 active+remapped+backfill_toofull 2020-10-29 
05:31:20.429912 610'549153 656:390372 [9,12] 9 [18,2] 18 594'547482 2020-10-25 
20:28:39.680744 594'543841 2020-10-21 21:21:33.092868
2.52 15 0 0 15 0 0 4883 4883 active+remapped+backfill_toofull 2020-10-29 
05:31:28.277898 652'502085 656:367288 [17,9] 17 [17,3] 17 594'499108 2020-10-26 
11:06:48.417825 594'499108 2020-10-26 11:06:48.417825


pool : 17 18 19 11 20 21 12 13 0 14 1 15 2 16 | SUM
--------------------------------------------------------------------------------------------------------------------------------
osd.4 3 0 0 0 9 2 0 0 12 1 9 0 7 1 | 44
osd.17 1 0 0 0 7 3 1 0 8 1 17 1 11 0 | 50
osd.18 0 0 0 0 9 0 0 0 4 0 7 0 5 0 | 25
osd.5 0 0 0 2 5 1 1 0 5 0 16 0 11 2 | 43
osd.6 0 1 0 1 5 2 0 0 9 0 13 1 7 0 | 39
osd.19 0 0 1 0 8 2 0 1 2 0 6 0 3 0 | 23
osd.7 0 0 0 0 4 1 1 0 3 0 12 0 19 0 | 40
osd.8 0 1 0 0 6 3 0 2 10 1 13 1 15 0 | 52
osd.9 1 0 2 0 10 2 0 0 4 1 6 1 10 0 | 37
osd.10 0 0 1 1 5 2 0 1 7 0 12 0 11 1 | 41
osd.20 1 0 0 0 6 1 0 1 7 0 8 1 17 0 | 42
osd.11 0 0 0 0 4 1 1 1 5 0 11 0 9 0 | 32
osd.12 0 0 1 1 7 1 0 0 5 1 12 1 14 1 | 44
osd.13 0 2 0 0 3 1 0 0 10 1 11 0 10 0 | 38
osd.0 0 1 0 1 6 3 0 1 7 0 11 0 13 0 | 43
osd.14 1 0 0 0 8 1 1 0 4 1 12 0 9 0 | 37
osd.15 1 0 2 1 6 1 1 0 8 0 7 0 6 2 | 35
osd.2 0 2 1 0 7 2 1 0 7 1 4 1 6 0 | 32
osd.3 0 0 0 0 9 0 0 0 2 0 4 0 5 0 | 20
osd.16 0 1 0 1 4 3 1 1 9 0 9 1 12 1 | 43
--------------------------------------------------------------------------------------------------------------------------------
SUM : 8 8 8 8 128 32 8 8 128 8 200 8 200 8 |
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