A virtual machine fails to power on with the error: Thin/TBZ disks cannot be opened in multiwriter mode. VMware ESX cannot open the virtual disk for clustering.

Symptoms

Summary

A virtual machine fails to power on with the error: 

Thin/TBZ disks cannot be opened in multiwriter mode. VMware ESX cannot open the virtual disk for clustering.

Example

Reason: Thin/TBZ disks cannot be opened in multiwriter mode..
Cannot open the disk '/vmfs/volumes/4c549ecd-66066010-e610-002354a2261b/Windows Server 2008/Windows Server 2008.vmdk' or one of the snapshot disks it depends on.
VMware ESX cannot open the virtual disk, "/vmfs/volumes/4c549ecd-66066010-e610-002354a2261b/Windows Server 2008/Windows Server 2008.vmdk" for clustering. Please verify that the virtual disk was created using the 'thick' option.

Impact

The virtual machine fails to power on.

Resolution

This issue usually occurs in configurations where a virtual disk is shared across multiple virtual machines.

The shared virtual disks must be in the eagerzeroedthick disk format to facilitate clustering configurations, such as Microsoft Clustering service and VMware Fault Tolerance. This issue occurs if the disk is not in the correct format. To verify if a virtual disk is zeroedthick/eagerzeroedthick, see Determining if a VMDK is zeroedthick or eagerzeroedthick (1011170).

To resolve this issue, see:

• Enabling clustering features for an existing virtual disk by converting in place (1035823)
• Enabling clustering features for an existing virtual disk by converting while copying (1003491)

Source of this Info:-

http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=1033570