Virtual machine hard disk shows 0B in vCenter

Products

• VMware vSphere ESXi

Issue/Introduction

• When editing a virtual machine’s settings in vCenter, one of the hard disk size appears as 0B (0 bytes).
• The affected virtual machine is currently running on a snapshot.
• Following error in the vSphere Client:
  
  Cannot open the disk '/vmfs/volumes/<datastore_name>/<vm_name>/<vm_name>-000001.vmdk' or one of the snapshot disks it depends on.
Reason: The parent virtual disk has been modified since the child was created.

Environment

VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x
VMware vSphere ESX 9.x

Cause

When the virtual machine references a virtual disk, it cites either the base disk's descriptor file, or a snapshot delta's descriptor file. A CID mismatch ensures that deviance from the original disk state results in all dependent child delta content being invalidated.

Resolution

1. Following kb "The parent virtual disk has been modified since the child was created" error to correct the Content ID mismatch
   1. Reviewing the .vmdk descriptor files of both the snapshot and parent disks.
   2. Verifying that the parentCID in the snapshot’s descriptor matches the CID of its parent disk.
   3. If mismatched, correcting the parentCID manually (only after proper validation and backup).
2. Run the following command on the ESXi virtual machine folder to inspect the virtual disk chain:
   
   vmkfstools -q -v10 <vm_name>-000001.vmdk
   
   This command will trace the snapshot hierarchy and show each parent/child relationship. Ensure that the snapshot chain is continuous and no “File not found” or “Inconsistent parent” messages appear.