Dear all,

How should ceph react in case of a host failure when from a total of 72 OSDs 12 
are out?
is it normal that for the remapping of the PGs it is not following the rule set 
for in the crush map? (according to the rule the OSDs should be selected from 
different chassis).

in the attached file you can find the crush map, and the results of:
ceph health detail
ceph osd dump
ceph osd tree
ceph -s

I can send the pg dump in a separate mail on request. Its compressed size is 
exceeding the size accepted by this mailing list.

Thank you for any help/directions.

Kind regards,
Laszlo

On 29.05.2017 14:58, Laszlo Budai wrote:

Hello all,

We have a ceph cluster with 72 OSDs distributed on 6 hosts, in 3 chassis. In 
our crush map the we are distributing the PGs on chassis (complete crush map 
below):

# rules
rule replicated_ruleset {
         ruleset 0
         type replicated
         min_size 1
         max_size 10
         step take default
         step chooseleaf firstn 0 type chassis
         step emit
}

We had a host failure, and I can see that ceph is using 2 OSDs from the same 
chassis for a lot of the remapped PGs. Even worse, I can see that there are 
cases when a PG is using two OSDs from the same host like here:

3.5f6   37      0       4       37      0       149446656       3040    3040    
active+remapped 2017-05-26 11:29:23.122820      61820'222074    61820:158025    
[52,39] 52      [52,39,3]       52      61488'198356    2017-05-23 
23:51:56.210597      61488'198356    2017-05-23 23:51:56.210597

I have tis in the log:
2017-05-26 11:26:53.244424 osd.52 10.12.193.69:6801/7044 1510 : cluster [INF] 
3.5f6 restarting backfill on osd.39 from (0'0,0'0] MAX to 61488'203000


What can be wrong?


Our crush map looks like this:

# begin crush map
tunable choose_local_tries 0
tunable choose_local_fallback_tries 0
tunable choose_total_tries 50
tunable chooseleaf_descend_once 1
tunable straw_calc_version 1

# devices
device 0 osd.0
device 1 osd.1
device 2 osd.2
device 3 osd.3
....
device 69 osd.69
device 70 osd.70
device 71 osd.71

# types
type 0 osd
type 1 host
type 2 chassis
type 3 rack
type 4 row
type 5 pdu
type 6 pod
type 7 room
type 8 datacenter
type 9 region
type 10 root

# buckets
host tv-c1-al01 {
         id -7           # do not change unnecessarily
         # weight 21.840
         alg straw
         hash 0  # rjenkins1
         item osd.5 weight 1.820
         item osd.11 weight 1.820
         item osd.17 weight 1.820
         item osd.23 weight 1.820
         item osd.29 weight 1.820
         item osd.35 weight 1.820
         item osd.41 weight 1.820
         item osd.47 weight 1.820
         item osd.53 weight 1.820
         item osd.59 weight 1.820
         item osd.65 weight 1.820
         item osd.71 weight 1.820
}
host tv-c1-al02 {
         id -3           # do not change unnecessarily
         # weight 21.840
         alg straw
         hash 0  # rjenkins1
         item osd.1 weight 1.820
         item osd.7 weight 1.820
         item osd.13 weight 1.820
         item osd.19 weight 1.820
         item osd.25 weight 1.820
         item osd.31 weight 1.820
         item osd.37 weight 1.820
         item osd.43 weight 1.820
         item osd.49 weight 1.820
         item osd.55 weight 1.820
         item osd.61 weight 1.820
         item osd.67 weight 1.820
}
chassis tv-c1 {
         id -8           # do not change unnecessarily
         # weight 43.680
         alg straw
         hash 0  # rjenkins1
         item tv-c1-al01 weight 21.840
         item tv-c1-al02 weight 21.840
}
host tv-c2-al01 {
         id -5           # do not change unnecessarily
         # weight 21.840
         alg straw
         hash 0  # rjenkins1
         item osd.3 weight 1.820
         item osd.9 weight 1.820
         item osd.15 weight 1.820
         item osd.21 weight 1.820
         item osd.27 weight 1.820
         item osd.33 weight 1.820
         item osd.39 weight 1.820
         item osd.45 weight 1.820
         item osd.51 weight 1.820
         item osd.57 weight 1.820
         item osd.63 weight 1.820
         item osd.70 weight 1.820
}
host tv-c2-al02 {
         id -2           # do not change unnecessarily
         # weight 21.840
         alg straw
         hash 0  # rjenkins1
         item osd.0 weight 1.820
         item osd.6 weight 1.820
         item osd.12 weight 1.820
         item osd.18 weight 1.820
         item osd.24 weight 1.820
         item osd.30 weight 1.820
         item osd.36 weight 1.820
         item osd.42 weight 1.820
         item osd.48 weight 1.820
         item osd.54 weight 1.820
         item osd.60 weight 1.820
         item osd.66 weight 1.820
}
chassis tv-c2 {
         id -9           # do not change unnecessarily
         # weight 43.680
         alg straw
         hash 0  # rjenkins1
         item tv-c2-al01 weight 21.840
         item tv-c2-al02 weight 21.840
}
host tv-c1-al03 {
         id -6           # do not change unnecessarily
         # weight 21.840
         alg straw
         hash 0  # rjenkins1
         item osd.4 weight 1.820
         item osd.10 weight 1.820
         item osd.16 weight 1.820
         item osd.22 weight 1.820
         item osd.28 weight 1.820
         item osd.34 weight 1.820
         item osd.40 weight 1.820
         item osd.46 weight 1.820
         item osd.52 weight 1.820
         item osd.58 weight 1.820
         item osd.64 weight 1.820
         item osd.69 weight 1.820
}
host tv-c2-al03 {
         id -4           # do not change unnecessarily
         # weight 21.840
         alg straw
         hash 0  # rjenkins1
         item osd.2 weight 1.820
         item osd.8 weight 1.820
         item osd.14 weight 1.820
         item osd.20 weight 1.820
         item osd.26 weight 1.820
         item osd.32 weight 1.820
         item osd.38 weight 1.820
         item osd.44 weight 1.820
         item osd.50 weight 1.820
         item osd.56 weight 1.820
         item osd.62 weight 1.820
         item osd.68 weight 1.820
}
chassis tv-c3 {
         id -10          # do not change unnecessarily
         # weight 43.680
         alg straw
         hash 0  # rjenkins1
         item tv-c1-al03 weight 21.840
         item tv-c2-al03 weight 21.840
}
root default {
         id -1           # do not change unnecessarily
         # weight 131.040
         alg straw
         hash 0  # rjenkins1
         item tv-c1 weight 43.680
         item tv-c2 weight 43.680
         item tv-c3 weight 43.680
}

# rules
rule replicated_ruleset {
         ruleset 0
         type replicated
         min_size 1
         max_size 10
         step take default
         step chooseleaf firstn 0 type chassis
         step emit
}

# end crush map


Thank you,
Laszlo
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