As well as power and weight heat is another issue with high density installations which can be overlooked; I can give a shameless plug for HP here now I am no longer employed by them in that HP blades have low power consumption and heat output for the computing power they provide compared with their majior competitors.

Otherwise more air cooling has to be installed which ironically leads to more elctrical power being drawn by the datacentre.

I remember when I had to do some temp work (moving boxes) and it was in a data center, which happened to have two big rack things of blade servers back to back with each other, about 3m apart. I stood in between them and it was quite an experience, my hair blew everywhere ^_^

They should build all datacenters with swimming pools on the roof (away from the microwave dishes). Not only would this be an ideal heat-sink it would also provide something to do at lunch when you're 10 miles from the nearest pub.

It almost makes you pine for the good old days, when real computers were cooled with water (the IBM 3090) or Fluorinert (the backlit "waterfall" of the Cray-2).

The same thing has been said time and time again over the years as the boxes have shrunk and density per rack has gone up. Anyone installing or expanding their server racks without considering both the power consumption and heat generation (ie cooling requirements) is, as the headline suggests, an idiot - but there's nothing particularly special about blades, they are just the latest step in the trend towards ever higher density.

HP's blades are no cooler than the competition's. See for example

http://www.theregister.co.uk/2007/03/15/ibm_retort_blade/

In terms of performance per watt, Sun's systems clearly have the advantage:

http://www.sun.com/servers/coolthreads/t2000/

16 to 32 threads running at up to 1.4 GHz. Peak system power consumption ranging from 267W to 333W, depending on system configuration.

That compares with 216W for only a two processor blade system from HP:

ftp://ftp.compaq.com/pub/products/servers/blades/idc-tco-deployment.pdf

That's right, you read it here first... Turn your servers & IT Equipment OFF now or we all die!