One of the key features of Ceph is its self-repairing and self-healing qualities. Ceph does this by keeping multiple copies of placement groups across different OSDs and ensures very high probability that you will not lose your data. In very rare cases, you may see the failure of multiple OSDs, where one or more PG replicas are on a failed OSD, and the PG state becomes incomplete, which leads to errors in the cluster health. For granular recovery, Ceph provides a low-level PG and object data recovery tool known as ceph-objectstore-tool.
The ceph-objectstore-tool can be a risky operation, and the command needs to be run either as root or sudo. Do not attempt this on a production cluster without engaging the Red Hat Ceph Storage Support, unless you are sure of what you are doing. It can cause irreversible data loss in your cluster.
