Ceph performs extensive logging. In Chapter 4, Planning your the Deployment, we discussed the need to provision ample drive space to accommodate spikes in log volume and to allow healthy retention intervals. In Chapter 8, Ceph Architecture: Under the Hood we will explore the severity levels of Ceph's log messages.

Ceph can be configured to log directly through the central syslog or rsyslog service, but by default it writes to local files. These are managed by the stock Linux logrotate facility. Here's the default rotation stanza that the Ceph Jewel release installs.

# cat /etc/logrotate.d/ceph.logrotate/var/log/ceph/*.log {    rotate 7    daily    compress    sharedscripts    postrotate        killall -q -1 ceph-mon ceph-mds ceph-osd ceph-fuse radosgw   
            || true    endscript    missingok    notifempty    su root ceph}

The default retention is 7 days, which this author at times finds to be too short. To increase to four weeks, replace the 7 with 30, but be careful that the filesystem...