Building a fast low-power home server

In my home, I have a need for a fast NAS box that, while not in use, uses as little power as possible. My requirements are basically:

* 1 TB of harddisk space, mirrored (RAID-1).
* Fast NFS (possibly SMB) throughput (think >= 50 MByte/s).
* Always on: The server will run Tor, and should be reachable 24/7.
* Silent when not in use: Harddisks should be powered down when not in use.
* Economical when not in use: I am aiming for 10 W when not in use.
* Open and flexible: Should run a normal commodity OS (say: Ubuntu server), and write data to disk in an open format (so that, should be motherboard crash, I can connect the disk to another Linux system and read it).

The Qnap TS-209 Pro that I bought last year does not really fit the bill; Qnap cheaped out on the CPU, and put a Geode 800 (500 MHz) in, which results in the server being CPU bound at a NFS read/write rate of ~22/15 MByte/s.

The new system will be based on the very economical (let reasonably fast) VIA C7 line of CPUs. The mainboard (which comes as a package with a NanoBGA 1.8 GHz C7 on it) is a VIA EPIA SN-18000G. This mainboard has a low power usage when not in use, yet is reasonably fast. A really nice touch on this mainboard is that one can actually put a CF card in a slot on the bottom; I'll be using a CF card here to boot my system from, so that I can spin down the harddisks when not in use, but more on that in a later post.

Anyway, this is the hardware list:

* Mainboard/CPU: VIA EPIA SN-18000G w/ 1.8 MHz NanoBGA C7.
* 2 x 1 GB DDR2/PC5300 RAM.
* A Kingston Elite Pro 16 GB CF Card (SLC, for reliability).
* 2 x 1 TB WD10EADS "Caviar Green" hard drives.

The harddrives are notable for the fact that they have a < 3 W power usage when idle, and a ~0.4 W power usage when spun down.

I'll be assembling my system tonight... More info (including actual power-usage measurements) is on its way.