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Troubleshooting storage issues

A multi-attach storage error occurs when the mounting volume on a new node is not possible because the failed node cannot unmount the attached volume. A cluster administrator can resolve multi-attach storage issues by enabling multiple attachments using RWX volumes or recovering/deleting the failed node when using an RWO volume.

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=0

      This command deletes the volumes stuck on shutdown or crashed nodes after six minutes.