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VMware snapshot disks separated/error? PDF Print E-mail
Sometimes snapshots become separated from their parent disk files and VMs will no longer power up when this occurs. When this happens you will get an error message stating "Cannot open the disk vmname-000001.vmdk or one of the snapshot disks it depends on. Reason: the parent virtual disk has been modified since the child was created." This can occur when you cold migrate a VM with snapshots from one ESX server to another. While the snapshot files are also migrated with the VM, the CID numbers in the VMDK descriptor file can change. Fortunately there is an easy fix.

Every virtual disk has two VMDK files associated with it. The larger one will have -flat at the end of the name and is the actual raw data of the virtual disk. The smaller one is the descriptor file that contains some basic information about the configuration of the virtual disk. If you open the descriptor file for your original disk (which will usually named the same as your VM, i.e. myvm.vmdk) with a text editor such as Nano, you will see a CID and a parentCID listed. The parentCID of the first disk is always "ffffffff", notice in the example below that the snapshot parentCID does not match the CID of the original disk.

Original disk file:
CID=37b6f123
parentCID=ffffffff
Snapshot disk file:
CID=afafa03b
parentCID=ba4f9916
To rejoin the child to the parent edit the descriptor VMDK file of the snapshot, take the CID of the original disk file and change the parentCID of the snapshot disk file so they are the same, as below.

Original disk file:
CID=37b6f123
parentCID=ffffffff
Snapshot disk file:
CID=afafa03b
parentCID=37b6f123

This should 'rescue' your separated disks...

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