Unable to Unmount the Datastore, Unmount Option is Grayed Out

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms

• While attempting to unmount a Datastore in a VMware environment, the Unmount option is grayed out.

• When trying to unmount the Datastore via the command line, the following error message is displayed:

[root@ESXiHost :~ ] esxcli storage filesystem unmount --volume-uuid=664c717f-########-####-########e5dc
Volume '664c717f-########-####-########e5dc' cannot be unmounted. Reason: Busy

Environment

VMware ESXi 7.x

VMware ESXi 8.x

Cause

Upon reviewing the open processes related to the Datastore, it was found that the FDM (Fault Domain Manager) process was holding the lock.

[root@ESXiHost :~ ] lsof | grep -i 664c717f-########-####-########e5dc
21###27 fdm FILE 22 /vmfs/volumes/664c717f-########-####-########e5dc/.vSphere-HA/FDM-a2e42bae-####-####-####-########7eb8-14-db82386-FDC######VIP01/host-##-hb

The .vSphere-HA directory is a hidden folder used for storing information related to VMware High Availability (HA) management. The file host-##-hb represents a heartbeat file associated with the HA process (fdm) for a specific host.
The interaction of the fdm process with this heartbeat file prevents the Datastore from being unmounted, as the file remains in use.

Resolution

 

• Disable HA on the Cluster to release the lock on the Datastore.
  • Disabling VMware HA will stop its interaction with the heartbeat file, allowing the unmount operation to proceed.
    
    
• Unmount the Datastore successfully using the following command on all ESXi hosts:

[root@ESXiHost :~ ] esxcli storage filesystem unmount --volume-uuid=664c717f-########-####-########e5dc

• Rescan the storage cluster-wide after the Datastore has been unmounted across all hosts.

Notes:

• If the issue persists, ensure that HA is completely disabled and that no other processes are accessing the Datastore during the unmount operation.
• After unmounting, remember to re-enable HA on the cluster if required.