For what it's worth, I went with a LaCie 5big Thunderbolt enclosure. It exports five disks as just that and nothing more. You do all the RAID and everything in software. At that point, it's just another mounted filesystem and all your favorite backup tools will do the right thing. Obviously, this is a bit easier to wrangle on a Mac where you've got a Thunderbolt connector, but it looks like a PCIe Thunderbolt card can be had for well under $100.