CephNodeDown

1. Check Description

Severity: Error

Potential Customer Impact: Medium

2. Overview

A storage node went down. Please check the node immediately. The alert should contain the node name.

A node running Ceph pods is down. While storage operations will continue to function as Ceph is designed to deal with a node failure, it is recommended to resolve the issue to minimise risk of another node going down and affecting storage functions.

3. Prerequisites

3.1. Verify cluster access

Check the output to ensure you are in the correct context for the cluster mentioned in the alert. If not, please change context and proceed.

List clusters you have permission to access:
ocm list clusters

From the list above, find the cluster id of the cluster named in the alert. If you do not see the alerting cluster in the list above please refer Effective communication with SRE Platform

Create a tunnel through backplane by provdiing SSH key passphrase:
ocm backplane tunnel <cluster_id>
In a new tab, login to target cluster using backplane by provdiing 2FA:
ocm backplane login <cluster_id>

3.2. Check Alerts

Set port-forwarding for alertmanager:
oc port-forward alertmanager-managed-ocs-alertmanager-0 9093 -n openshift-storage
Check all alerts
curl http://localhost:9093/api/v1/alerts | jq '.data[] | select( .labels.alertname) | { ALERT: .labels.alertname, STATE: .status.state}'

3.3. Check OCS Ceph Cluster Health

You may directly check OCS Ceph Cluster health by using the rook-ceph toolbox.

Step 1: Check and document ceph cluster health:
TOOLS_POD=$(oc get pods -n openshift-storage -l app=rook-ceph-tools -o name)
oc rsh -n openshift-storage $TOOLS_POD
Step 2: From the rsh command prompt, run the following and capture the output.
ceph status
ceph osd status
exit

If 'ceph status' is not in HEALTH_OK, please look at the Troubleshooting section to resolve issue.

3.4. Further info

3.4.1. OpenShift Data Foundation Dedicated Architecture

Red Hat OpenShift Data Foundation Dedicated (ODF Dedicated) is deployed in converged mode on OpenShift Dedicated Clusters by the OpenShift Cluster Manager add-on infrastructure.

Related Links
Step 3: Check the links to identify the errors.

1) https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/4/html/troubleshooting_guide/troubleshooting-ceph-osds#common-ceph-osd-error-messages-in-the-ceph-logs_diag 2) https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/4/html/troubleshooting_guide/troubleshooting-ceph-placement-groups#inconsistent-placement-groups_diag

4. Alert

4.1. Make changes to solve alert

Document the current OCS pods (running and failing):
oc -n openshift-storage get pods

The OCS resource requirements must be met in order for the osd pods to be scheduled on the new node. This may take a few minutes as the ceph cluster recovers data for the failing but now recovering osd.

To watch this recovery in action ensure the osd pods were actually placed on the new worker node.

Check if the previous failing osd pods are now running:
oc -n openshift-storage get pods

If the previously failing osd pods have not been scheduled, use describe and check events for reasons the pods were not rescheduled.

Describe events for failing osd pod:
oc -n openshift-storage get pods | grep osd

Find a failing osd pod(s):

oc -n openshift-storage describe pods/<osd podname from previous step>

In the event section look for failure reasons, such as resources not being met.

In addition, you may use the rook-ceph-toolbox to watch the recovery. This step is optional but can be helpful for large Ceph clusters.

Determine failed OCS Node

Run the following to get the list of worker nodes and check for the node status:
oc get nodes --selector='node-role.kubernetes.io/worker','!node-role.kubernetes.io/infra'
Describe the node which is of NotReady status to get more information on the failure:
oc describe node <node_name>

Access the Toolbox

Run the following to rsh to the toolbox pod:
TOOLS_POD=$(oc get pods -n openshift-storage -l app=rook-ceph-tools -o name)
oc rsh -n openshift-storage $TOOLS_POD
From the rsh command prompt, run the following and watch for "recovery" under the io section:
ceph status

(Optional log gathering)

Document Ceph Cluster health check:
oc adm must-gather --image=registry.redhat.io/ocs4/ocs-must-gather-rhel8:v4.6

5. Troubleshooting

  • Issue encountered while following the SOP

Any issues while following the SOP should be documented here.