Verifying the integrity of the parent disks for an ESX/ESXi virtual machine

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

This article describes steps that can be taken to correct the situation of a virtual machine with a snapshot failing to power on when one of its parent virtual disks has been modified.

Symptoms:

• Cannot power on a virtual machine.
• Cannot open the disk or one of the snapshot disks it depends on.
• The parent virtual disk has been modified since the child was created.

Resolution

When a snapshot is taken of a virtual machine, a new (redo) virtual disk file is created for each of its original (parent) virtual disks and any changes made to its virtual disks are written to the new virtual disk files. VMware determines the current data written to each virtual disk by examining the difference between the parent virtual disks and the redo virtual disks. For the virtual machine to continue to function, the parent virtual disk files cannot be modified.

If a parent disk is modified, you are not be able to power on the virtual machine. This situation can only be corrected in one of the following ways:

Note: The following procedures must all be done when the affected virtual machine is powered off.

Caution: VMware recommends that you backup up the entire virtual machine before attempting any of the following procedures.

Note: For information on locating virtual disk files, see Verifying that ESX virtual machine storage is accessible (1003751).

1. Restore the parent virtual disk files from a backup taken when the virtual machine functioned.
   
   Note: The parent virtual disks can be identified as all files that end in .vmdk but do not end in -00000x.vmdk , where x is a number.
   
   
   
2. Restore all of the virtual machine files from a backup taken when the virtual machine functioned.
   
   Caution: Doing this results in the loss of any data that was changed since the backup was taken.
   
   
3. Remove the snapshot:
   
   Caution: Doing this results in the loss of any data that was changed since the snapshot was taken.
   
   
   1. From the virtual machine's directory, delete all files that end in .vmsn , .vmsd , .vmss and -00000x.vmdk , where x is a number.
   2. From the virtual machine's directory, delete all files and folders that end in .lck .
   3. Edit the virtual machine's configuration (.vmx) file.
   4. Look for any entries that include -00000x.vmdk, where x is a number, and delete -00000x , leaving the rest of the entry intact.
   5. Save the edited version of the .vmx file.