Notes from the Consultant's Jungle

The process for drafting indicative pricing for data center IT installations typically follows a predicable path.  First, the configuration of IT kit is examined for expected power dissipation.  With the power estimates in hand, cooling and physical space estimates can be drafted.  With power, cooling, and space estimates, one can propose rack configurations for candidate cabinet power density levels on the computer room floor.  At the end we have what we need to get vendor quotes for the IT equipment and the impact on the data center (or quotes from collocation providers).

Cost Contribution of Cabling

One component that often goes unchecked, even during deeper rounds of data center cost estimation is the cost of cabling.  Cabling costs can be (usually are) rather significant, especially with the escalating price of copper.  While through the 90’s, data center planners considered the cost of copper as data centers require vast amounts in support of “below white space” and “above white space” infrastructure, since 2005 the price of copper has been a dynamic variable that added a new complicating factor to data center implementation budget planning accuracy.

In the figure, we can see that the price of copper has now returned to double 2005 levels, after softening during the 2008 recession.

Cabling is overlooked during data center cost estimation, sometimes because of simple neglect, or confusion over how to price without a detailed parts list.  Rules of thumb or market rates are usually known for the other areas of cost estimation, but what about cables?

In this article, I will share with you a method that I use to include cabling costs of data center implementations even when there are very few “knowns” regarding the ultimate solution.

Dollars per RU Model

Many data center architects will base high level power dissipation estimates on the number of Rack Units (RU’s) occupied by the IT kit.  The recent BICSI-002 standard, in fact, recommends such an approach.  A similar approach can be taken for estimating cable costs.  Because equipment specifications may not be sufficiently detailed to know port count, interface type, and precise location in rack elevations, the total number of occupied RU’s can be used as a starting metric.

Because the cost of cabling will ultimately be impacted by port speed, media type, cable types, and lengths, we will use a range for estimation.  It is up to the engineer’s judgment, given their understanding of the IT environment at the time, to select where in the range to declare a cost term.  We suggest the range be from $250 per RU to $500 per RU.  The idea is to multiply the total number of occupied RU (the number of Rack Units that are consumed by the inventory of IT equipment) by a value from the range above, selected based on the estimator’s notion of complexity.  The resulting value is the indicative cost estimate for cable materials including cable management hardware.

We would be very interested to hear your perspectives and experience with using this model in your own work.  Please write back and share your experiences.