For starters, never try to mount one half of a RAID1 array without mdadm (the software raid you will be using on Ubuntu) being present. It handles how the two drives sync up so if you mount and alter (access times count as altering) one disk, mdadm has a real challenge to work out what's gone wrong. It could result in needing to rebuild the array or even data loss.
I was going to suggest you have a virtual machine (Ubuntu Server is very light) that mounted the partitions directly (as modern VMs can) so you're using the same version of mdadm as your install of Ubuntu. It's fairly sound logic but it's a lot more flimsey than a native install because you have a software layer between Ubuntu and the disks.