Some notes about Ceph
Laurent Barbe @CCM Benchmark

Change log level on the fly to Ceph daemons

Aaahhh full disk this morning. Sometimes the logs can go crazy, and the files can quickly reach several gigabytes.

Show debug option (on host) :

# Look at log file
tail -n 1000 /var/log/ceph/ceph-osd.33.log

# Check debug levels
ceph daemon osd.33 config show | grep '"debug_'
    "debug_none": "0\/5",
    "debug_lockdep": "0\/1",
    "debug_context": "0\/1",
    "debug_crush": "1\/1",
    "debug_mds": "1\/5",
    "debug_filestore": "1\/5",

In my case it was about filestore, so "ceph tell" is my friend to apply the new value to the whole cluster (on admin host) :

ceph tell osd.* injectargs --debug-filestore 0/5

Now you can remove the log file on reopen it :

rm /var/log/ceph/ceph-osd.33.log

ceph daemon osd.33 log reopen

Then it will remain to be added in the ceph.conf file (on each osd hosts) :

        debug filestore = 0/5

For more information from ceph documentation : http://docs.ceph.com/docs/master/rados/troubleshooting/log-and-debug/