Ceph subsystems

Understanding Ceph subsystems and their logging levels

Ceph consists of several subsystems.

Each subsystem has a logging level:

• Output logs that are stored by default in /var/log/ceph/ directory (log level)

• Logs that are stored in a memory cache (memory level)

In general, Ceph does not send logs stored in memory to the output logs unless:

• A fatal signal is raised

• An assert in source code is triggered

• You request it

You can set different values for each of these subsystems. Ceph logging levels operate on a scale of 1 to 20, where 1 is terse and 20 is verbose.

Use a single value for the log level and memory level to set them both to the same value. For example, debug_osd = 5 sets the debug level for the ceph-osd daemon to 5.

To use different values for the output log level and the memory level, separate the values with a forward slash (/). For example, debug_mon = 1/5 sets the debug log level for the ceph-mon daemon to 1 and its memory log level to 5.

Ceph Subsystems and the Logging Default Values

Example Log Outputs

The following examples show the type of messages in the logs when you increase the verbosity for the Monitors and OSDs.

debug_ms = 5
debug_mon = 20
debug_paxos = 20
debug_auth = 20

Example Log Output of Monitor Debug Settings

2022-05-12 12:37:04.278761 7f45a9afc700 10 mon.cephn2@0(leader).osd e322 e322: 2 osds: 2 up, 2 in
2022-05-12 12:37:04.278792 7f45a9afc700 10 mon.cephn2@0(leader).osd e322  min_last_epoch_clean 322
2022-05-12 12:37:04.278795 7f45a9afc700 10 mon.cephn2@0(leader).log v1010106 log
2022-05-12 12:37:04.278799 7f45a9afc700 10 mon.cephn2@0(leader).auth v2877 auth
2022-05-12 12:37:04.278811 7f45a9afc700 20 mon.cephn2@0(leader) e1 sync_trim_providers
2022-05-12 12:37:09.278914 7f45a9afc700 11 mon.cephn2@0(leader) e1 tick
2022-05-12 12:37:09.278949 7f45a9afc700 10 mon.cephn2@0(leader).pg v8126 v8126: 64 pgs: 64 active+clean; 60168 kB data, 172 MB used, 20285 MB / 20457 MB avail
2022-05-12 12:37:09.278975 7f45a9afc700 10 mon.cephn2@0(leader).paxosservice(pgmap 7511..8126) maybe_trim trim_to 7626 would only trim 115 < paxos_service_trim_min 250
2022-05-12 12:37:09.278982 7f45a9afc700 10 mon.cephn2@0(leader).osd e322 e322: 2 osds: 2 up, 2 in
2022-05-12 12:37:09.278989 7f45a9afc700  5 mon.cephn2@0(leader).paxos(paxos active c 1028850..1029466) is_readable = 1 - now=2021-08-12 12:37:09.278990 lease_expire=0.000000 has v0 lc 1029466
....
2022-05-12 12:59:18.769963 7f45a92fb700  1 -- 192.168.0.112:6789/0 <== osd.1 192.168.0.114:6800/2801 5724 ==== pg_stats(0 pgs tid 3045 v 0) v1 ==== 124+0+0 (2380105412 0 0) 0x5d96300 con 0x4d5bf40
2022-05-12 12:59:18.770053 7f45a92fb700  1 -- 192.168.0.112:6789/0 --> 192.168.0.114:6800/2801 -- pg_stats_ack(0 pgs tid 3045) v1 -- ?+0 0x550ae00 con 0x4d5bf40
2022-05-12 12:59:32.916397 7f45a9afc700  0 mon.cephn2@0(leader).data_health(1) update_stats avail 53% total 1951 MB, used 780 MB, avail 1053 MB
....
2022-05-12 13:01:05.256263 7f45a92fb700  1 -- 192.168.0.112:6789/0 --> 192.168.0.113:6800/2410 -- mon_subscribe_ack(300s) v1 -- ?+0 0x4f283c0 con 0x4d5b440

Example log output of OSD debug settings