Unable to Unmount VMFS Datastore with "Reason: Busy"

Products

• VMware vCenter Server
• VMware vSphere ESXi 7.0

Issue/Introduction

When attempting to unmount a VMFS datastore using the `esxcli` command, the operation fails with the message:  
`Volume 'Datastore-Name' cannot be unmounted. Reason: Busy`

[root@server01:~] cd /vmfs/volumes/Datastore-Name/

[root@server01:/vmfs/volumes/xxxxxxxx-xxxxxxxx-xxxx-xxxxxxxxxxxx] 

[root@server01:/vmfs/volumes/xxxxxxxx-xxxxxxxx-xxxx-xxxxxxxxxxxx] esxcli storage filesystem unmount --volume-label=Datastore-Name
Volume 'Datastore-Name' cannot be unmounted. Reason: Busy

 

Environment

ESXi 7.0

Cause

This error indicates that the datastore cannot be unmounted because there are currently active processes or operations utilizing it. 
Common reasons include:

1. Virtual Machines are accessing the datastore – A VM might be running or have a virtual disk located on the datastore.
2. Active file system locks – Processes like file management or backup tools could be accessing files on the datastore.
3. Storage-related operations – Operations like storage vMotion, snapshot creation, 
   or other storage maintenance tasks could be preventing the unmount operation.

Resolution

1. Identify active VMs on the datastore:
   Use the `esxcli` command to list VMs using the datastore:

   #esxcli vm process list
   
   This will show any running VMs that may have their virtual disks on the datastore. 
   If you find any VMs using the datastore, power them off or migrate them to a different ESXi or different datastore.

2. Check for active files or open files.
   You can use the following command to check if there are open files on the datastore UUID:

   #lsof | grep /vmfs/volumes/xxxxxxxx-xxxxxxxx-xxxx-xxxxxxxxxxxx
  
   This will list processes that have files open on the datastore. 
   If any World name like "sh" related processes are listed, you will need to identify and terminate them.
   As the Symptoms description, the datastore unmount failed due to root user locked "/vmfs/volumes/xxxxxxxx-xxxxxxxx-xxxx-xxxxxxxxxxxx" direcotry,
   and this issue can be resolved by change the shell working directory from VMFS root volume to other location:
   
   [root@server01:/vmfs/volumes/xxxxxxxx-xxxxxxxx-xxxx-xxxxxxxxxxxx] cd /

   [root@server01:~] esxcli storage filesystem unmount --volume-label=Datastore-Name

3. Check for ongoing storage operations:
   Check for any ongoing storage-related operations, such as storage vMotion or backup tasks, which could prevent unmounting. 
   These operations can be monitored in the vSphere Client.