Unable to grow or expand a VMFS volume or datastore
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Unable to grow or expand a VMFS volume or datastore

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Article ID: 313382

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Updated On: 03-06-2025

Products

VMware vSphere ESXi VMware vSphere ESXi 7.0 VMware vSphere ESXi 8.0

Issue/Introduction

When trying to grow or expand a VMFS volume by clicking Increase Capacity, no drives are being displayed or not the desired drives are showing up.

 

Environment

ESXi 7.x
ESXi 8.x

Cause

Potential Causes preventing a successful grow/expansion of the VMFS volume or datastore:

  • To increase the capacity (grow or extend) of a VMFS datastore successfully, ensure that the device has been increased from the backend SAN
  • Once completed, initiate a cluster level rescan to ensure that the Extent Device list contains updated list and then use the Increase option
  • If the device for which size is increased from backend SAN is exposed to multiple hosts in multiple clusters, then cluster level rescan has to be triggered on all the clusters where device is visible
  • Also ensure that the LUN ID is same across all the cluster hosts
  • Please ensure there are no partition on the existing LUNS which are being added to the datastore
  • No drives or not the desired drives are being displayed when clicking Increase Capacity. Reason: Only drives matching the same Disk Sector Format as being used by the affected VMFS Datastore are being displayed. The Disk Sector Format can be checked by running via SSH/Putty:
vdq -q | grep -iE "Name|FormatType"
 
"Name"                : "naa.550550550550"       --> VMFS Datastore
"FormatType"    : "512n",
"Name"                : "naa.889988899889"       --> Drive which is planned to use for extending the VMFS Datastore
"FormatType"    : "512e",
 
--> In this example we do see that both drives are not having the same Disk Sector Format.
Therefore "naa.889988899889" will not be displayed when clicking Increase Capacity because it cannot be used for extending the datastore.
References: 
vSphere 7.0
 

Resolution

After the cause has been identified and resolved, the Capacity of a VMFS datastore can be expanded via the following ways:

 
A.) Via vCenter Web Client:
 
1.) Initiate a Cluster level rescan (incase the device is shared across multiple hosts/clusters) or on the host (incase of a stand-alone host) so as to force the ESXi host(s) to sync in with the change for the underlying devices expansion.
If the device for which size is increased from backend SAN is exposed to multiple hosts in multiple clusters, then cluster level rescan has to be triggered on all the clusters where device is visible.

2.) Right click on the cluster/host and select Storage > Rescan Storage.


 

2.) Navigate to the Datastore View and select the Datastore
3.) Navigate to Configure > Device Backing and select the Extent Name



You should be able to see the Device Details reflecting the update capacity basis the expansion done from the SAN.

Note: 
In this example, the datastore iscsi1 was configured for 250 GB and the underlying device was expanded to 400 GB. 
If the underlying device is not reflecting the updated info, attempt a cluster/host level rescan once again so that the fields highlighted in the image above indicate the desired change.
 
 
The following steps would need to be followed ONLY if you are able to detect an increase in the capacity of the underlying device.

 

B.) Via Host Client:

1.) Log in to one of the hosts that has access to this datastore via the GUI (host client) using the root credentials. Navigate to Storage > Datastores and select the datastore in question.
2.) Right click on the datastore and select Increase Capacity. Alternatively, select the option at the top to perform the same (highlighted in green).

 
3.) You would be prompted to select one of the two options. Add an extent to existing VMFS datastore or Expand an existing VMFS datastore extent. 
Note:
The first option is to create multi-extent datastores by spanning (adding) a new volume to the existing datastore and
the second option is to increase the capacity for the existing device itself. In this example, proceed with the second option. 
 

4.) You should be able to view the device extent as indicated in the screenshot below. Select the device instance and click Next.



5.) Select the VMFS partition as highlighted in the image and use to side-scroller to indicate the range of the expansion that would need to be done and click Next.
Once completed, click on Finish. You should now be able to view the datastore expansion having completed successfully.

6.) Considering this expansion activity was directly on the host by bypassing the vCenter Server.
VMware recommends that once the expansion is completed at the host level, a Cluster level rescan is initiated so that all the hosts that have access to this datastore are in sync with the expansion that was just recently performed. 
Note: 
If a Cluster level rescan is not done from the vCenter Server level, there are good chances that the vCenter Server might not readily detect the change
and there would be a disparity in the current space/usage for the datastore in question.
VMware recommends that a Cluster level rescan at the vCenter Server level is always followed after any form of expansion being done at the host level.  
 

7.) You should be able to view the datastore reflecting the updated capacity uniformly across the vCenter Server.

 

Additional Information

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