5.7. Troubleshooting storage issues
5.7.1. Resolving multi-attach errors
When a node crashes or shuts down abruptly, the attached ReadWriteOnce (RWO) volume is expected to be unmounted from the node so that it can be used by a pod scheduled on another node.
However, mounting on a new node is not possible because the failed node is unable to unmount the attached volume.
A multi-attach error is reported:
Example output
Unable to attach or mount volumes: unmounted volumes=[sso-mysql-pvol], unattached volumes=[sso-mysql-pvol default-token-x4rzc]: timed out waiting for the condition Multi-Attach error for volume "pvc-8837384d-69d7-40b2-b2e6-5df86943eef9" Volume is already used by pod(s) sso-mysql-1-ns6b4
Procedure
To resolve the multi-attach issue, use one of the following solutions:
Enable multiple attachments by using RWX volumes.
For most storage solutions, you can use ReadWriteMany (RWX) volumes to prevent multi-attach errors.
Recover or delete the failed node when using an RWO volume.
For storage that does not support RWX, such as VMware vSphere, RWO volumes must be used instead. However, RWO volumes cannot be mounted on multiple nodes.
If you encounter a multi-attach error message with an RWO volume, force delete the pod on a shutdown or crashed node to avoid data loss in critical workloads, such as when dynamic persistent volumes are attached.
$ oc delete pod <old_pod> --force=true --grace-period=0s
This command deletes the volumes stuck on shutdown or crashed nodes after six minutes.
