I've recently installed Windows Server 2012 to my test server to run Hyper-V test environment. I have bunch of old VMs which were created in Windows Server 2008 R2 Hyper-V which I didn't export in advance – I just have all VMs files created on old server.
I was able to successfully import VMs with fixed VHD, but unable to do it with those which use differencing disks – import wizard unable to handle this. Most of my old VMs using differencing disks tied to one parent VHD.
Any advice on how to import them into Hyper-V 3.0?
Best Answer
Don't think you can import differencing disks. For this disk type, differences are stored in the differencing disk, which starts with no data, and grows to store the unique data. The parent disk also will have lots of Input operations because it is the source or common denominator. This is not suitable for personal/assigned VDI VMs or server VMs because you cannot upgrade/resize the parent and inherit the changes; you have to delete the lot and start again. As a general best practice, always backup your VMs before making configuration changes. Please check out http://www.altaro.com/hyper-v-backup/ for effective Hyper-V backup.