320Gb is definitely more than needed, but look at the disks on the site; the smallest drive there is an 80Gb Western Digital, but it costs £29.10; the 320Gb Seagate costs £28.66. /shrug Hey, if they want to charge less for a 320Gb than a smaller drive, I'll take the 320Gb.

As to the 850W, darn right I don't need all of it right now, but (a) I want the PSU nowhere near its limits when running two RAID arrays; and (b) I'll be adding in disks in the future to increase storage space as needed; I don't want to have to buy another PSU or worry about stressing the PSU at that point. It's relatively cheap future-proofing.

Few notes from someone who's built way to many home, and other, servers.

You made the right call on the drive, low end hard disk prices hit a wall pretty hard which leaves them looking a bit silly.

You're vastly overestimating the amount of power required to run the disk arrays, even at peak spin-up loads. The only way you could fit enough hardware into that chassis to come near using that PSU is multiple high-end GPUs.

If you're going to build a home server it's almost always worth investing in an AC power meter if you don't already have one.

Nearly every PSU operates most efficiently somewhere in the middle of it's power range, operating a high power PSU at 20% capacity will use notably more power than a correctly sized one. Take a look at any PSU review over at silentpcreview.com, they do good efficiency testing.

> Nearly every PSU operates most efficiently somewhere in the middle of it's power range, operating a high power PSU at 20% capacity will use notably more power than a correctly sized one.

One note from a physics major who's first job out of college was a the electrical officer on a frigate: this applies to all electrical devices. This sort of "over-supply solves all problems" attitude is quaint when it's a home server. It really sucks when under-loaded 1MW diesel generators shit the bed almost weekly on deployment in the summer. Any idea how much hot-dark-and-quiet sucks when you're bobbing like a cork in the middle of the ocean in the summer? Now imagine you're the person that 250 hot, cranky people expect to fix it. Why? because some "contracting expert" in the Pentagon decided to "over-spec" the generators 25 years ago.

Niels, the PSU in this build actually does operate most efficiently in the 40%-60% load region according to its specs; it wasn't just a rule-of-thumb.

Also, the lower you load it, the easier it gets to cool, according to its own specs. Which I take as a nice bonus.

Do you really save anything significant by purchasing less than 320GB, these days?

It's gone up - you're talking a difference of pence between the 320Gb and 500Gb versions of the same drive these days.

I've been shopping, recently, and while I'm not looking in that size range, the prices in that range that I've happened to notice align with what you're saying, the the extent I recall. (For me, in the U.S.)

The exception, I guess, might be for extremely fast platter drives or for SSD's. (And with platter drives, you're still to some extent up against speed by virtue of rotation speed versus speed by virtue of data density.)

FreeNAS works really well on a little 1GB USB stick - dedicating ALL of the SATA connectors to disks.

Won't the write load of log files and things eventually kill the flash chips? USB sticks are made from pretty bottom-of-the barrel parts...

This can be dealt with by putting /var on the SATA disks, but at that point I wonder how much you're saving using the USB stick rather than a mirror on the cheapest drives you can find of reasonable quality.

FreeNAS actually recommends you install the OS on a flash disk (whether that's a 3.5 or a USB stick doesn't matter) so that the disks can be reserved entirely for storage.