How did we get to the modern data centre design?  Why do most data centres look the same? Why are they so inefficient in how they consume electrical power? Why do they typically have a raised plenum floor and air handling units that keep air at fixed temperature ranges and humidity levels?

I guess the first time I saw a data centre in the flesh was at University, we had an ICL System 4, a very new ICL 1900 and some DEC Programmed Data Processors (PDP) computers.  They all had open reel tape drives, some had removable cartridge disks and the operators were skilled workers who had a pretty deep understanding of what was going on.

(Do you know the origin of the term debugging? In the days of electronic valves, small insects would move into the electronics and nest.  As they died, their bodies would decay giving causing shorts and opens in the primitive circuitry.  Operators used to debug their computers with a dustpan and brush, removing the detritus of dead bugs).

Some of the drivers for data centre design then were:

The need to reduce dust particles (as these caused head crashes on the cartridge disks and read write errors on the open reel tapes).

The need to maintain the same temperature during tape read operations as during tape write operations so that the tape did not expand or contract and cause data errors!

The raised floor was useful in that it enabled the huge numbers of proprietary and enormously thick cables that joined the main processor to the input output devices to be hidden from view and reduce trip hazards.

So Engineers looked at the constraints and designed a building that mainly recirculated air round and round the room so that external air contamination could be kept out.  Remember in the 1970s most data centres were in City centres and the main form of heating in the UK was coal.

Recirculating air meant that they needed to introduce artificial cooling so refrigeration units were installed in the airflow to maintain temperatures at a steady 20 - 24 degrees Celsius (68 - 74 degrees Fahrenheit).  Cold aid blowing creates cold surfaces so they had to deal with condensation and potentially very dry air and static discharges and as a result humidifiers were introduced.  (Static electricity can destroy delicate computer circuits).

The crazy thing is that even though the technical requirements have changed out of all proportion most data centres still look the way I remember in 1974.