Sorry,
I'm not here that much lately and usually other experts pop-in to help.
--> What OS?
In all honesty what I'd do is build a NAS using FreeNAS and a low power board/CPU combo that can handle a Gigabit LAN connection and a RAID card.
Takes the RAID load off the 'work machine'.
Easier on work machine's power supply.
Reduces heat in work machine's case.
Moves drive noise away from the desk.
Contrary to opinions created by effective marketing gimmicks, a 3GB/sec is no advantage over slower interfaces.
Head to Disk Transfer Rate of the drives (not the Interface's speed) is the 'real' limit except during bursts.
High End 7200 RPM drives max out at around 80 MB/sec but ~60MB/sec is more typical.
Assuming a Stripping form of RAID,, 2x80 MB/sec = 160 MB/sec [Sustained Xfer rate.]
Current drives (even 10k RPM) can't even fill the bandwidth for 1.5GB/sec.
All a faster interface does is fill up the buffer faster. - Rather useless.
160 MB/sec through a Gigabit LAN is no problem at all.
An old 1GHz P3 server board with PCI-X slots is more than adequate to handle FreeNAS with RAID and Gigabit LAN. They are cheap and fairly easy to find.
They usually support dual CPU's but you only need one CPU for FreeNAS.
[Tip: Tyan and Intel brand boards of that vintage don't have the capacitor problems that many other brands did back then.]
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Dual Xeon socket 603 and 604 boards with 400 or 533 MHz FSB will also do it and are getting cheap to build but the CPUs will pull 2x to 3x the power of a ~35 watt P3.
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