The first thing you should ensure is that your network is gigabit capable so bottlenecks shouldn't happen. And gigabit switches and Cat 6 cabling aren't that costly.

@swenkruiper,

But what if part of the OS of the NAS is that it formats any drives it first encounters, as an automatic feature, when the drive is first entered into the NAS?

This is the case with my HP NAS and it is part of the OS that was with the machine when I bought it. Granted, I suppose I could have changed the OS and used a Linux OS instead of the Windows Home Server that came with it, but then there goes the warranty. And since I'm new to the idea of using a NAS I still have some studying to do, as well as some upgrading of the machine to seriously consider, I have come to realize.

But wait... is that "format a newly inserted drive" part of the OS, or is it part of the NAS's BIOS? HP doesn't explain any of that in their literature.

Whatever the case, if I did as you outlined, I think I would find myself with a set of newly formatted drives with no data on them at all. So I figure that one's best bet is to build his own NAS from standard parts and put it together with good software, learning something very useful in the process.

Start with a case (3 - 5 1/4 bays needed) and micro-ATX mobo, add a 5-disk RAID cage (about $120) and Linux OS to drive it. There are NAS-specific Linux systems out there; you only have to search for them. Or you can buy Windows Home Server software. But I don't know if you can customize it like you can a Linux server system. I have also run across systems with more than 5 drives, but they cost upwards of a thousand dollars, so you are getting into enterprise-level storage costs.

If you're in need of this level of backup security, you should seriously consider the enterprise-class of SATA hard drives and not use anything bigger than 1TB. A 2-terabyte drive take 24 hours plus to format! I shudder what 3TB would take. And at the quantity of drives needed (3 at a time: 1 for data, 1 for mirror and 1 for emergency backup (needed on-site and immediately) if one of the primaries fail), they would be cheaper.