Avoid software RAID then. We use that and it works decently well but took a lot of frustration to get going.

A hardware RAID on the other hand, can present multiple disks to the operating system like a single hard drive. Configuring which drives are part of an array often becomes an extended CMOS setting completely independent of the installed OS: you might get a 'press ESC to configure drives' message on boot before the OS actually loads. Assuming your server is a PC that is. It's not so much that they're not designed to work with UNIX, as much as they may not have bothered writing UNIX device drivers. This may not be as important as it used to be (for PC hardware, anyway) since most disk controllers are AHCI-compliant these days and work fine with a generic driver. That's a pretty important question... "UNIX" is a completely generic term; Your wireless router might be running a kind of UNIX. So do most supercomputers. Obviously you can't run software from one on the other or fit hardware from one into the other. In a shell, try uname and uname -a to find out what your system is.

That alone won't tell you what kind of card slots this server has and which, if any, are free, so you might need to take a look at the hardware itself too. Mostly, interface. SATA-II? SATA-III? SCSI? Probably you want SATA I think. SATA hotswap cages are cheap these days. Exactly. The permissions, timestamps, users, and everything else all get bundled up along with the files when you make a tar with -p. Formatting it in NTFS is necessary for Windows if the drive came with FAT, because FAT can't hold files larger than 4 gigabytes. Good deal. We tried to go cheap and tried a jmicron controller, which caused some (fortunately recoverable) data corruption. Never again.

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Also: A RAID isn't exactly a backup. It's tempting since it's automatic and improves your speed too. It somewhat protects you from a single-disk failure -- that's all. (And single-disk failiures will occur more often because you're running more disks.) Any other kind of problem -- an out-of-control program, dying disk controller, murderous power supply, fire, lightning strike, utility company, theft, volcano -- are still quite capable of swallowing your data entire. A trustworthy backup is when you make a copy and mail it somewhere else.