Troubleshooting migration compatibility warning: Device uses backing which is not accessible
Symptoms
When performing a VMotion migration the following compatibility warning is displayed:
Unable to migrate from <source server> to <destination server>: Device '<device>' uses backing '<device>', which is not accessible .
Resolution
Overview
This unable to migrate warning message indicates that the virtual machine has a device that is disconnected and pointing to an image that is not accessible on the destination host.
The possible devices that can show this warning are:
CD ROM Drive
Floppy Drive
This warning can be safely ignored and only appears if you are using an image file (ISO, FLP, etc.) and not a physical device.
Workaround
To workaround the issue, perform on of the following actions:
Ensure that the image being used in the device is accessible from all ESX Servers by storing the files on a datastore that is shared between all ESX Servers and participate in VMotion of the virtual machine.
Edit the settings of the virtual machine and configure the drive to use the client device before performing a migration.
