Via Web Client: VM shows increased Storage consumption after adding thin provisioned RDM disk

Products

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

Issue/Introduction

An RDM Disk was added to an existing VM.
The RDM Disk is thin provisioned.
Despite the fact the allocated space has not been used yet, the Web Client is showing the space provided by the added RDM disk under "Storage", 
raising the question on whether these 600 GB are already considered as being used.

Following Screenshots show an example of such a VM.

The VM shows 688.1 GB after a 600 GB RDM disk (thin provisioned) has been added, while its OS is reporting the 600 GB as Unallocated:

 

 

Environment

ESXi 7.x

ESXi 8.x

Cause

This is by Design.

The VM reports all the space that is allocated to it. 

In the Example shown above: After adding to an existing 89 GB, a 600GB RDM disk, the VM is reporting ~ 689 GB.

Resolution

This is not an issue. This is per Design.

We can verify that the space consumption has not increased after adding the RDM disk

by comparing the outputs from prior and after adding the RDM disk 

by running the following command:

du -sh