One more vote for StarWind V2V. I have done multiple successful P2V conversions. Following article was helpful
If I understand you right, you want to use your old 1TB drive to backup data from new 2TB. Yes, it would be possible, to partition it that way (if it is needed). You can avoid it using some kind of a backup solution. However, the amount of space on an old drive would be an issue here.
I've had multiple cases open with Asus RMA about 4 years ago and never had such weird answers. Meh, support went wrong direction. I would agree that contacting their social channels should help you getting a RMA request fulfilled.
I have a Hyper-V cluster in my lab. For a shared storage I am utilizing StarWind VSAN over iSCSI. Local storage is RAID10 HDDs. Each server has dual port 10GbE card for cluster and iSCSI traffic great performing and stable setup.
Depending on your NAS (and its iSCSI stack) you can play with it...
You can replace disk 1, for example, wait for the rebuild and then proceed with the next one. Repeating this, you will recieve RAID6 array with 8TB drives, but with old usable capacity (cause the controller will be using only half of the capacity of your drives).
I would recommend you create...