An existing RDM virtual disk cannot be provisioned to a virtual machine within the vCenter environment.

Products

• VMware vSphere ESXi

Issue/Introduction

Connecting RDM disks to a Primary virtual machine works fine. However, when attempting to add these existing RDM virtual disks to the secondary VM, these disks are not listed as available disks to add in the add disk wizard.

Environment

VMware vSphere vCenter 8.x

Cause

vCenter datastore browser reveals an incorrect object type presentation: the RDM descriptor file and its corresponding flat file are displayed as generic files. The virtual disk or the pointer of the RDM LUN marked as generic files instead of virtual disks. 

Virtual disks show up as generic files in vCenter GUI. This happens because one or more ESXi host sends incorrect information to the vcenter about the RDM pointer/virtual disks.

Resolution

To address the virtual disk display discrepancy:

1. An existing disk should be attached to the virtual machine via the host GUI.
2. The ESXi host that is reporting the virtual disk as a generic file must be identified by logging into the host GUI or from the commandline. 
3. Subsequently, either the affected LUN should be unmounted/detached from that specific host as a workaround, or reboot the host to fix the issue.
4. After host reboot, please login to the host GUI and check if host is displaying the RDM pointer as virtual disks and verify the same from the vcenter GUI.