I know the topic is old but I think it's worth writing about. I'm currently using Unraid OS 7.0.0-beta.3
I wanted to replace the motherboard and processor so I prepared screenshots of disk assignments and other settings, then I turned off the server and started to move the hardware. One thing I didn't do was disable automatic start of the array (I forgot).
I installed new components, connected the disks randomly to SATA ports and started the server. Imagine my surprise when the array simply started up. Each disk was in its place and everything simply started up. The array works as before the upgrade, the dockers started up, everything started up as after a regular restart.
As you can see, it can be done without problems