RE: Expand virtual disk size in Raid 1.
You can only reconfigure a RAID 1 to RAID 5 by adding a third (or more) disk.
You said the old disks were 500GB, replaced with 1TB drives, and that you should be seeing 1.8G (2TB). That can ONLY be the case if you reconfigured the RAID 1 to a RAID 0 (DON'T do this!).
What exactly do you have and what and where are you seeing it?