The Twin Towers of Soekris

Recently we bought some Soekris net6501 computers to replace our aging 4801s.

However, the 19" rack case doesn't come with fans, and the litte Atom processor runs quite hot - the core temperature exceeds 80°C even when idle and when I stacked two of them on top of each other for the first tests, they reached the critical temperature of 90°C and clocked down.

This runs too hot.

Propping it up on two boxes didn't help: Air insulates at least es well as wood.

Not much better.

But then I had an idea: The cases are designed to have fans mounted on the sides, but without those fans there is little horizontal air flow. But they are narrow and long — if you put them vertically, you should get a nice chimney effect:

Cool but wobbly.

And it worked nicely. The warm air from the motherboard and the power supply escaped through the holes on the top and cool air was sucked in through the holes at the bottom. You could even feel a slight draft. I also tried both positions: First with the power supply at the bottom, then with the power supply at the top.

Core temperature.

As expected, having the power supply at the top is best: The cool air flows first over the motherboard, where it is heated, then trough the power supply, where it is heated further, and then warm air escapes out of the top vents. This gives us another 4°C advantage over having the power supply at the bottom. In total, about 14°C difference to the horizontal position.

Of course this configuration is sowewhat top-heavy: Not only is the heaviest part, the power supply, at the very top, the motherboard and almost all of the cables are also in the upper half. I didn't dare to leave it standing like this over the weekend (even though earthquakes are rare here).

So I needed a more stable arrangement. A bit of doodling with LibreCAD, and some time spent cutting away at some thick cardboard later (I should have used the Lazzzor — that kind of work seemed much less exhausting when I was a kid) I had something I considered stable enough:

One soekris in its cardboard stand.

The final two node Soekris cluster will then look like this (except with a lot more cables and blinkenlights):

Two node cluster configuration — the Twin Towers of Soekris.