CephMdsMissingReplicas

Minimum required replicas for the storage metadata service (MDS) are not available. MDS is responsible for filing metadata. Degradation of the MDS service can affect how the storage cluster works (related to the CephFS storage class) and should be fixed as soon as possible.

Impact: High

Diagnosis

pod status: pending
  1. Check for resource issues, pending Persistent Volume Claims (PVCs), node assignment, and kubelet problems, using the following commands:
    • oc project openshift-storage
    • oc get pod | grep rook-ceph-mds
  2. Set MYPOD as the variable for the pod that is identified as the problem pod, specifying the name of the pod that is identified as the problem pod for <pod_name>:
    Examine the output for a {ceph-component} that is in the pending state, not running or not ready
MYPOD=<pod_name>
  3. Look for the resource limitations or pending PVCs. Otherwise, check for the node assignment, using the oc get pod/${MYPOD} -o wide command.
pod status: NOT pending, running, but NOT ready
Check the readiness of the probe, using the oc describe pod/${MYPOD} command.
pod status: NOT pending, but NOT running
Check for application or image issues, using the oc logs pod/${MYPOD} command.
Important: If a node was assigned, check the kubelet on the node.

Mitigation

(Optional) Debugging log information
Run the following command to gather the debugging information for the Ceph cluster:
oc adm must-gather --image=registry.redhat.io/ocs4/ocs-must-gather-rhel8:v4.6