How to change a Ceph configuration dynamically?

Environment

• Red Hat Ceph Storage 1.2.3

• Red Hat Ceph Storage 1.3

Issue

• Is it possible to change a Ceph configuration or tunable without restarting the Ceph cluster or OSDs and MONs?

Resolution

• Configuration changes can be injected to the Ceph cluster dynamically.

• This process will force the Ceph cluster to update/change the configuration settings/value without a restart.

• In order to change the setting dynamically, use:

# ceph tell mon.* injectargs '--{configurable value}' 

• For example, to change the the 'mon_osd_full_ratio' dynamically, use:

# ceph tell mon.* injectargs '--mon_osd_full_ratio 0.99'

• To confirm if the change has indeed taken place, use :

# ceph daemon /var/run/ceph/ceph-mon.{hostname_-s}.asok config show | grep mon_osd_full_ratio

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