In a previous post, I presented the CFM-00, a “cluster” of 8 Pentium III at 500MHz, assembled into one MDF casing. The assembly was rather clean-cut given the rather rudimentary materials (MDF and threaded rods) but the resulting computing power is dismal (but that’s no surprise). We have about 2GHz of computing power, and at 128MB of ram per node, it makes running even just a remote shell not that responsive.
A few months ago, my friend Christopher came to me with a data center clearing deal with Pentium III 1GHz 1U rack-mount (with 512MB of RAM) servers for $15, and I got eight of them to build the CFM-01, the successor to the CFM-00. But I did not strip the motherboards from their casing this time, I built an inexpensive rack out of slotted angle steel.
Slotted angle steel can be bought from any home improvement store for about $2 per foot, and is strong enough to support the weight of 8 1U servers, a switch, and a power bar.
But rather than having the servers laid out horizontally (as you would with a commercial rack) I opted for a simpler “hanging” strategy—especially as the deal did not include rails for the servers. Hanging the servers only asks for a rather simple box design: the interior of the frame should be (about) 17¾” wide. Length is not that important, it has to accommodate whatever you need; a 1U unit is exactly 1¾” thick. I set length to 24”.
The height of the rack is 30”, so it’d be roughly the same height as my desk, but that’s up to you: maybe higher is more convenient. You need at least 24” so that the servers do not touch the ground and so that you have some room for the power and network cables (as neither are very good at bending 90°).
The rest is simple: you cut the slotted steel angle to desired lengths and spray-paint them black. Or bright pink. Whatever you want. Once the paint is dry, you assemble them using ¼” 20 bolts and nuts. They’re also rather inexpensive and you can get them by boxes of 50 for something like $5. You need bolts, nuts, and cut washers to make it really strong. You’ll need 24 sets, 3 per corner. I assembled the corners with the bolts using a ratchet (and a titanium drill bit as sometimes there’s simply no way to align the slotted steel angle holes).
And voilà, you’re done!
Well, almost: you still have to put your servers in and connect all cables. Personally, I like to use tie-wraps to fasten cables to the frame so that they do not dangle and that everything looks rather neat.
The total cost of the thing is about $250, all included. The power bar and switch (24 ports at 100MBits/s) I got from the Montreal Computer Surplus. The web site doesn’t look like much, but the guy keeps an absurdly large quantity of spare parts and not quite up-to-date hardware. There are good deals for anyone who wants to build a cluster like the CFM-01. Cables are still expensive, as I needed only cat-5 (and not cat-5e) I could’ve got them from the local dollar store, but I got them from Papeterie & Cie, a local office supplies store.
In hindsight, I should have extended the vertical bars a bit above the front panels so I could have built a shelve on top to put a monitor and keyboard. Oh well, maybe for the CFM-02.