DCN April 2016 - Page 42

structured testing come on avoiding panic and accidents or is there a period of pitch black? The design may have several minutes of autonomy in the UPS and batteries to maintain the IT systems but does the cooling continue at a sufficient level to prevent overheating of the IT systems? Test cause and effect, for example when the fire alarms are set off do you want the security doors to unlock or remain locked? Should the cooling be shut down or the fresh air ventilation be closed off? Move the heat load around Massive amounts of energy can be wasted by lightly loaded systems. This can result in a very slow ramp up of IT load, if it ever achieves the design load. If the design team has assumed rapid ramp up of load and IT capacity is correct, they may have designed the data centre in such a way that causes significant problems with the operation. In some circumstances if the IT load is low UPS and generators will not hold the load or cooling cannot be managed effectively. Massive amounts of energy can be wasted by lightly loaded systems. It is optimistic to expect a recently commissioned data centre to go from 0 to 100 per cent of capacity at the flick of a switch. We recommend 42 starting with a load of no more than 10 per cent, allowing the facility to stabilise before moving on to the next incremental step increase. Really test your data centre When a new airport terminal or cruise ship is handed over to the customer they run exhaustive testing before opening to the public. This involves armies of volunteers or members of staff mimicking the processes the public will go through. Some of the testing will be destructive testing. What happens when the lifts all fail? Can the stairs cope with a sudden influx of passengers rushing to their departure gate? If all of the passengers rush over to one side of the ship will it cause instability to the ship? Can the fresh and dirty water systems cope with every toilet being flushed simultaneously? The same is true in your data centre. Test everything. When the power fails and the generators are starting does the emergency lighting Over the design life of the data centre IT will go through several technology refreshes, this could result in hotter or cooler systems being deployed. As space is occupied the original layout may no longer be valid. IT system’s technical limitations may dictate a higher density layout than expected. Several of our customers test their data centres with several layouts; A uniform load, with heat load spread evenly throughout the data centre. A varied load to try to represent the predicted IT load layout, with different racks having differing heat load capacities uneven, worst case load scenario with the majority of the heat load in one or more rows of racks with very little heat load in the rest of the data centre. Regression testing During testing, problems will be discovered that require a fix to resolve the situation. The temptation is to apply the fix, complete the failed test and move on to the next test. The risk is that the ‘fix’ may have inadvertently invalidated previous tests. It is imperative that the fix be fully investigated and any previous tests that could be affected be rerun.