I'm looking to add an external RAID1 array to my iMac for some peace of mind. I need an absolute bare minimum of 3 TB (so 2 x 3 TB), but at least 4 TB is what I am really looking for. More would of course be nice but it seems that drive prices increase pretty rapidly past 4 TB per drive (even the price per TB looks to increase past 4 TB), and since I need two drives things could quickly get very expensive. USB 3.0 is fine since this is mostly for backup purposes, but a Thunderbolt connection would be nice if it doesn't considerably increase the price. The Western Digital MyBook Duo 8TB (the standard USB 3.0 version, not the Thunderbolt one) is going for just $325 right now which is an incredible deal. It's actually a bit cheaper than a 2-bay RAID enclosure and a pair of 4 TB drives. Is there any reason not to just go with this over a bare RAID enclosure and getting the two hard drives separately? I've built PC's before and have also built Linux servers with RAID1 and RAID10 arrays, so any set-up complexity isn't a problem. Any recommendations on a RAID enclosure would also be great -- I've only dealt with internal RAID arrays and it's been a few years since I've built a server, so I'm not up to date with what's available now. I'm trying to keep total costs under $500.