Unable to expand a VMFS datastore via the vSphere Client or the ESXi client

Products

• VMware vSphere ESXi
• VMware vSphere ESXi 7.0
• VMware vSphere ESXi 8.0

Issue/Introduction

 

After expanding the LUN backing the datastore, in the vCenter client, the Increase Datastore Capacity wizard does not present the storage device with available space:

Environment

VMware vSphere ESXi Storage 7.0
VMware vSphere ESXi Storage 8.0

Cause

This issue occurs if the datastore is force mounted.

On a "force mounted" datastore the size cannot be increased  ( Datastore expansion )

Note: Force mounting also prevents a LUN being automatically mounted when presented to new hosts, and, in general, should be a temporary measure.

To identify a force mounted datastore please see:  Identify if a datastore is force mounted on an ESXi host

 

Resolution

To resolve this, the datastore needs to be re-signatured which will change the UUID of the datastore

To re-signature a force mounted datastore, the datastore needs to be unmounted from all ESXi hosts. 

To unmount the Datastore, the IOPS on the Datastore should not do IO operations which needs ,

• Migrate all the VM(s) off the Datastore 
  
  
• Shutting down all the VM(s) and unregister from ESXI ( make a note of VM and VMX files ) 

To re-signature a snapshot/replica LUN (the volume is mounted immediately after the re-signature with a new UUID,), run this command:

• Please note the steps and warnings outlined in the Additional Information before executing this command.
  esxcli storage vmfs snapshot resignature -l label|-u uuid

• For example:
  esxcli storage vmfs snapshot resignature -l "VMFS_1"
esxcli storage vmfs snapshot resignature -u "########-########-####-############"
  
  
• To (persistently force) mount a snapshot/replica LUN across reboots, run this command:
  esxcli storage vmfs snapshot mount -l label|-u uuid
  
  
• To (noN persistent force) mount a snapshot/replica LUN that is not persistent across reboots, run this command:
  esxcli storage vmfs snapshot mount -n -l label|-u uuid

For detailed steps, impacts and best practices on how to resolve force mounted LUNs, please see the following KB Troubleshooting LUNs detected as snapshot LUNs in vSphere

 

Additional Information

When extension of a force mounted datastore is attempted from the vSphere Client, the partition table on the LUN may be extended (although the filesystem is not grown).

In that case, after the LUN is re-signatured, and the Increase Datastore Capacity wizard is run again, no available space is detected on the LUN. If this occurs, please engage Broadcom support to assist in completing extension of the datastore from the command-line

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See the below KB for alternative reasons why you may be unable to expand a datastore via the vSphere Client:

Extending or increasing a datastore through vCenter Server fails