multi boot - Should I make partition when setting up a RAID-1?

If I want to do RAID-1, and I also want to boot several different OSes (Windows 7, Linux) for example, should I perform the following steps?

1. Create RAID-1 Mirror from BIOS.


2. Use GParted to create several partitions.
   _{(I believe under GParted, I will see two disks, under which one should I create the partitions then?)}


3. Install Windows and then Ubuntu?

Or is it better to create RAID-1 and install RAID-1 on the whole disk first, then resize the partition later for Ubuntu?