The CERC SATA 1.5/6CH is a 1.5Gbps (SATA I) controller, so it would be a waste to get SATA II or III, unless they are the same price or cheaper (likely) and/or they will be repurposed at some point.   Yes, each array is treated individually and separately, so you can have two RAID 1's of differing (or the same) drive size ... you can even have a RAID 1 and a RAID 5. The Best Practices that I linked to in my last post is probably he best (and the only I could find) documentation on it: [URL]  
I have a PowerEdge 830 (running SBS2003) w/ an XD084 6ch SATA controller. It currently has 2 x 250GB drives. I'd like to upgrade the server to SBS2008 and create a larger RAID1 configuration (using 1TB or larger drives). Can you tell me what configuration options/limitations are available w/ this controller? Thanks.
Expanding drives w/ Adaptec XD084