I have an Asus P8P67 motherboard which is running Win 7. I have two pairs of WD HDDs running as RAID-1 pairs, using Intel RST :
Disk 0 : 2 x 2TB - used for data
Disk 1 : 2 x 500GB - used for the operating system. This contains 3 partitions:
100MB - System reserved, flagged as System, Active and Primary Partition
465 GB - Boot, Crash Dump and Primary Partition
449 MB - Unallocated
Currently I am using 280GB of the 500GB and 875GB of the 2TB.
My plan is to replace the 500GB with a 1TB SSD.
Potentially, to replace the 2TB with SSD in the future.