Putting your foot flat on the accelerator doesn’t make for an efficient data center

The sheer complexity of new data center builds that respond to external conditions etc have meant that the traditional skills of the operation team cannot be relied on to squeeze the maximum efficiency out of their new or upgraded facility. Some far-sighted design engineers now invite the operations team to the Integrated Systems Test (IST), but we don’t feel this goes far enough.

The IST is normally the final project before handover and tests the entire facility under design conditions and normally includes:

·         Turning the load up to design, then failing the utility feed to check power is maintained by the UPS while the generators start and continue to supply full power.

·         A "heat run" test - the application of the full design load on the raised floor by using resistive load banks (often by using sets of fan heaters in racks to take the place of servers).

·         Next, air conditioning units are shut down, one-at-a-time, to reflect redundancy levels. For example, if the redundancy of computer room air conditioning units (CRAC) is one out of four, then one out of four units is shut down until every combination of on/off units is tested.

The IST is generally the last point at which major issues in a data center can be remedied. After the sign-off, the cost of remediation falls on the operator and once ‘live’ there may be no opportunity to make the required changes.

What we have observed in a number of sites, some at IST and others once operational is that the site controls have been implemented and configured only to pass the IST i.e. without consideration of the energy and cost performance of the site in the majority of its working life. It’s a bit like testing your car by accelerating to its top speed – this won’t give any indication of its miles per gallon performance or how it handles in the rain.

Following this, one of the key services that we’ve introduced for our customers is a secondary test to be run immediately after the IST and before the site is accepted. We call this the “Performance Validation Test” (PVT) and it covers whether the site operates in the way it is intended to.

This involves running the site at part load and, preferably forcing cooling changes such as free cooling to mechanical. During these tests the overall and sub-system level performance of the site is recorded and compared with the expected performance of the design based on the topology, selected devices and intended control configuration. It also predicts the data center TCO and PUE at part load and specifies what the critical meters should actually be reading in non-critical situations.

Not only is this PVT useful for tuning your data center to adapt to real-life conditions, it allows the operations team the ability to understand what tools they have their command to increase efficiency as IT load changes.

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