Latest rig is designed to blow all hot air UP. Giving convection a helping hand, so to speak.
Check the middle shelf - there are three domestic extractor fans screwed in there - they are 240V devices and the fans blow air UPWARDS. The idea is that all hot air will either exit out of the GPU bracket grilles (i.e. the bits that the air *should* exit from if they were in a PC case) or sideways out of the tops of the cards. This will be resisted by fans blowing air *inwards* at those points. A test with a desk fan blowing directly at the open case worked fine.
The idea is mainly to provide an enclosed box that can be used as furniture... and then the exorbitant electricity bill I get in the UK from this lark (four figures a quarter) will be sufficient to heat my house as well
The previous design had the GPU fans trying to suck air *down* onto the horizontal cards - fighting thermodynamics. And, unsurprisingly, it didn't work too well.
The latest design works very well indeed... it'd work even better with more fans on the middle shelf, since the outlets are only 100mm and the cards between the three fans run hotter than the cards directly above any of the fans.
I'm happy with it, it has a few duff design features (getting to the ethernet ports is a bitch) but it's tidy and high-density. Not much floor space for a fair amount of hashing power (around 4 GH/sec, lightly overclocked, giving around 1.95 MH/W efficiency).
Once I've finished this one (doors, additional input fans) and investigated whether my girlfriend and I can sleep with the rig sitting outside the bedroom on the landing (where it needs to be to heat the stairwell around the first floor area)... I'll use the old shelf rig to build another with the remaining boards, though it won't be anywhere near as powerful since I only have one 6950, four 5830s and all my old 5770s left
Will be quieter though
As to control features, I've written monitoring software in Ruby for a laugh - it spits out bits of HTML so my main web server can patch them together to show the entire mining farm status in one table. And of course, all miners (except the 6870 I chucked into my Mac Pro main workstation for teh lulz... and *worked* woah) are Linux so SSH from my iPhone / iPad / airbook or any handy unix-based device will let me sort them out if necessary. OK, Windows too, assuming Putty is installed