Julian Kudritzki: The tier system serves to take data centers, which are by definition highly customized, unique facilities, and compare them using a common set of concepts. We look purely at the design and its implementation, we don't look at what kind of building you have or how you staff it. Not that those aren't important but we start by asking, what are the maintenance opportunities and what is its fault response.

IDGNS: Meaning, how often do you have to take systems offline for maintenance?

J.K.: Right, or do you have to take them offline at all. One of the big leaps is between Tier 2 and Tier 3, because when you introduce Tier 3 you introduce maintenance opportunities across all the infrastructure without influencing your IT operations.

Then fault response, which comes with Tier 4, is the ability for the infrastructure in and of itself to rectify a faultcontain it and sustain the IT operations without any adverse impact.

IDGNS: What trends have you seen in the past few years?