Mini-Mac Server as an NAS

I have been wanting to start digitalizing my music and placing it on a server.
I have a Mini Mac Server that I have been using for my business that I am replacing with a Windows Server (the programs we run are Windows based and the problems that we have had with the software to convert Macs to virtual Windows Machines have been so problematic that that they have almost closed us down). I was wondering about using the Mini Mac as a home NAS, since I would like to get some use out of it and since I otherwise have a Mac based system at home.
My main concern is this: I need about 4TB, and the Mini mac Server has 1 TB, configured as 2 500 MB drives in a RAID config. Can I add extra drives
and have them work seamlessly?
07-30-11: Almarg
I'll add that I recently installed an external (USB) Western Digital advanced format drive on a Windows XP system, without using the alignment utility, and its speed as measured with HD Tune was as good as I would expect from any USB-connected drive.
I should have mentioned in this statement that prior to performing the speed measurement I had re-formatted the drive into multiple partitions, using Windows XP, which defeats the alignment the drive was originally supplied with, and supposedly makes it necessary to use the WD alignment utility. But no speed compromise resulted, even though I didn't use the utility.

-- Al
Al, notice there were no performance numbers in the marketing mumbo jumbo. For audio file storage, there is really no problem because it's basically sequential write once, then sequential reads. Anything that leans more towards random reads, and especially random writes, stick with "regular" drives if performance is somewhat critical or more so. That being said, these drives won't be used in "enterprise" class systems or arrays - at least the products I work on won't be using them - where performance counts.

I just read the last few posts after the one I commented on. No surprise about the USB based drives showing little or no impact on performance. My original comments reflected my own experience with the drives which is not comsumer PC home use. Although, as a purist, I still wouldn't use them at home because there is still extra overhead using the drives. And since I don't have to pay for disk drives, I can use the best available... :)

you can pull the superdrive and expose the sata connector and turn it into an esata and then run that to a 4-5 drive estata enclosure externally... the new lion os has the option to be a server or a workstation... your choice for $29...

Stick with Firewire on the Mac if you don't go this route... WD makes a 2 and a 4 drive external drop in drive setup for firewire.