I'm not certain I'm asking this in the right forum, so apologies if I've got it wrong. A quick search hasn't turned anything up either...

I'm looking to build, as per the title, an always-on ultra-low-power file server. My requirements are pretty flexible, but they currently look like this:
- Lowest possible power – the only really immutable requirement;
- 1TB storage;
- RAID5;
- SATA disks;
- 1Gb Ethernet;
- Linux (with Samba to share the disk as SMB);
- Headless, accessed by ssh;
- Fanless.

Forgive me if some of these questions seem a bit dumb – I have some experience of building my own boxes, but they’ve all been pretty standard builds before…

I guess I’m not going to need much processor grunt for this. Several people have suggested looking at Mini-ITX, but I’ve also seen a few boards like this one:
http://www.ampltd.com/prod/u886.html
or this one:
http://www.electronicspecifier.com [...] 70-SBC.asp
These (apparently) claim much lower power consumption than most Mini-ITX (1.5W typical against 9ishW typical).

I’d probably be looking for a system that could support wake-on-lan – in fact, I’ll try to employ every power-saving trick I can. I suppose I’m unlikely to find onboard gigabit Ethernet, so I’d need a dedicated card. I thought that I could consider putting the OS on a flash drive. I guess I’d probably be looking at a dedicated RAID controller. I have a tower case I can use to hold all this – not bothered if there is a mass of free space inside – that will help with cooling.

Disks: would 2.5” laptop disks be a better bet than 3.5” disks?

Budget is not a constraining factor – it’s more about the playing around to build this than tryingf to find a cheaper solution than already exists. Having said that, I don’t intend to buy the most expensive components just because I can – I’ll just probably choose performance (particularly in the low-power arena) over price.

Any comments/suggestions?

Thanks in advance – Adam…

Proximon - thanks for the reply...

I hadn't considered bus widths - good point. I'll investigate further, but any more info (or places to point me to for info) would be appreciated. I've only worked with motherboards that provided everything I needed in terms of buses in the past, so I've never really considered these things.

I'd happily consider a passive cooling system for hard disks, but they may still rely on active airflow. Ideally, I'd like this system to be as quiet as I can get, but if I have to stick a big case fan in, I can't see that being a big problem - it should only need to be on for short periods, and most of the 120mm case fans are very quiet and only seem to draw between 1 and 1.5 watts, which is pretty acceptable...

Cheers!

I kind of doubt you can run RAID5 on those motherboards. You would be better off with a separate RAID controller (if necessary) and RAID0 or RAID1.

For what you want, very unlikely that it will be fanless. Good quality 120mm fans are virtually silent while supplying ample cooling. Micro-ITX mobos typically do not have the expansion slots necessary to house a RAID Controller and/or a dedicated GigaE NIC. You mention money is not an issue, but a good micro-ITX board for what you want can cost $300-$400.

Your best bet here is a to get a micro-atx mobo with at least 1-16x PCIe slot and onboard video. Wake-on-LAN and onboard GigaE will depend on what mobo you choose. A mobo with the Intel 945G chipset would be a good choice and range in price from about $45-$75.

You will also want a dedicated PCIe RAID controller card with at least 4 SATA ports. For 1TB storage in RAID5 you're looking at at least 3-500GB drives. You can plug the RAID Controller card into the 16x PCIe slot to ensure maximum bandwidth anf no lag on file sharing/data transfer. Use the onboard video rather than a video card. I would recommend anything 3Ware or Areca. Some thing like this...3Ware 9650SE-4LPML

Intel makes a 35watt Celeron, but even this power-sipper will require active cooling, again choose an aftermarket heatsink with a good 120mm fan. The Celeron 430 would be a good choice.

If you want to install the OS on a Compact Flash card rather dedicating a seperate hard drive, I highly recommend you check out FreeNAS. FreeNAS has all the file sharing services you could ever want or need and is small enough to be loaded onto and run off a 512MB CF card.

Good luck!

Chunkymonster - thanks for loads of info!

No need for onboard video - I'm assuming this will be headless. The choice of the small form factor was only an attempt to save power - I'd happily use a standard ATX board if I could get one with low-enough power consumption. Ultimately, unless I'm missing something, all I need is: basic processor; memory; RAID controller (plus, therefore, PCI/PCI-E); GigaE (with capacity for wake-on-LAN); OS drive (flash?); cooling and that's all.

So, if it doesn't have onboard GigaE, my mobo just needs a processor socket, memory slots and 2 PCI slots (NIC and RAID). How would I connect a flash boot drive? USB?

Do the smaller form factors use a standard northbridge/southbridge architecture?

FreeNAS - that's absolutely brilliant, thanks - looks like precisely the OS I'm after.

Forgive me if I'm wittering a bit - I'm working stuff out as I type!

Incidentally, for reference, $300-$400 for a motherboard that does exactly what I want would barely make me blink (particularly as I'm in the UK, where US$400 barely buys you a cappuchino these days!!).

Thanks again - Adam...

evongugg - good point about the CPU and maybe I should be approaching it from that end instead. That is, what is the minimum CPU (and RAID card spec) that I could expect to run, say, 4 x 500GB SATA disks in a RAID5 configuration, such that the processor is not the bottleneck? What about if it's 5 x 500GB in a RAID 6?

Point taken about video output for setup. I assume onboard video would consume no power if disabled in the BIOS, or is that just being naive? Otherwise, a video card (I have at least one lying around somewhere) would be better as I can physically remove it when I don't need it.

Also, is it fair to assume that a PCI (or whatever) card would consume more power than an onboard interface? For example, I assume that a PCI GigaE would consume more power than an onboard one, even if it's a tiny difference - is that a reasonable assumption to make?

Cheers again!