ID #1104

The parent virtual disk has been modified since the child was created

VMware displays or popsup an error messages like this


Cannot open the disk test-000001.vmdk or one of the snapshot disks it depends on.
Reason: The parent virtual disk has been modified since the child was created. 

Platform :  any



There are several possible reasons for this message:
- a vmdk was used with a second VM
- unwise manual edit of the vmx-file
- unwise operations with vmware-vdiskmanager or vmkfstools
- failed operations with snapshotmanager
- bugs, host crashes ....
- buggy backup-software especially on ESX
- and finally the most probable : user-mistake

In all this cases the only thing that is sure is that something went wrong.
As long as you do not know what exactly was the reason ....

- do not trust the settings in the vmx-file
- do not trust the snapshot list in the vmsd file
- do not assume that 000002.vmdk is a child of 000001.vmdk and so on
- do not trust the person who reports the error


To analyse the case inspect all vndk descriptions that may have been in use by the snapshot-chain.
- Look up the child to parent filename-hints.
- Look up the CID-chain.
- Read all last logs.

Then when you have all this info make an educated guess on the most probable reason for the damage.
Once you understood what went wrong you should be able to guess how the snapshot-chain should look like.

Read about the CID-chain here and an example on how to fix it here
In case you use a vmdks and snapshots with embedded descriptor - read this first.  


Plan B


In case a VM with snapshots does not start anymore because a basedisk was expanded you have two options:
- undo the expand of the basedisk
- expand the snapshot
The second option only makes sense with VMs that only have one snapshot - I would not recommend this
In most cases it is very probably easier to undo the expand of the basedisk.

Tags: cid, error, parentfilenamehint

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