Friday 5 November 2010

How do you calculate the PUE for that...?

PUE is a ratio of power used effectively against power delivered to an organisation such as a data centre. In concept it is simple, but the process of calculating a real figure is fraught with complexities, assumptions and varying interpretations.

Calculating a PUE for a trading floor is not always easy. Not a lot of the equipment has individually metred power, so any figure calculated tends to be quite approximate. It does however bring back memories of a company where I used to work. One branch of the company was located in two floors of a multi-tenanted building. Our company had grown by a process of acquisition of other trading firms. A consequence of that was the the IT infrastructure and the supporting building services infrastructure was quite fragmented.

The business decided it could improve the level of trading by building and implementing a new trading floor within the existing building. Plans were duly made and agreed with the landlord. It was not until later in the project that it was realised the building electric power supply would need to be upgraded to meet the power demands of the new trading floor and its associated equipment. The directors of the business were not best pleased with the additional expense on the project but agreed the (new) premises manager could contact the utility company (via the landlord) to ask for additional power cables to be installed.

The shocking news (unintentional pun) came back from the power company. "Sorry guys but we cannot deliver that level of power to your building unless we build a high voltage sub-station." The price quoted would have shocked NASA. Eventually after much discussion it was decided our company would install its own high voltage sub-station in the building. Our company took on the role of supplying power to the other tenants from our sub-station. We had to recruit an additional facilities manager who was trained and certified in the operation of high voltage equipment. Needless to say the project went over budget! I was not the project manager - phew!

Calculating PUE on the basis of power supplied to our company would be interesting to say the least.

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