Unable to expand a VMFS datastore via the vSphere Client or the ESXi client
Article ID: 371313
Updated On:
Products
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:
Cause
This occurs if the datastore is force mounted.
A force mounted datastore cannot be increased in size.
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. This will require migrating all VMs from the datastore or shutting down and unregistering them.
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
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
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