I recently brought a 8708EM2 LSI megaraid card. I attached two 2TB drives and created
a RAID1 array with a 2TB virtual drive inside it.
Since I wanted to have a 4 disk RAID 5, I added one more drive to the card and migrated this "Drive group" from a "2 drive RAID 1" to a "3 drive RAID 5"...