From warehouse to (data)warehouse: Virtus keeps it cool in North London

Each of the datahalls is situated on the second floor of the datacentre while the machinery and equipment needed to run and maintain the servers is located on the floor below. 

Virtus provides the floor space in the datacentre for clients to rent and operate from, and clients are asked to bring their own hardware that they can put into dedicated data halls, private suites, cages areas or cabinet deployments.

The eight self-contained data halls at the Enfield datacentre can accommodate a total of 1,070 racks when they're at full capacity. 

The Virtus facility has a PUE of 1.48. 

PUE expresses the proportion of power that must be expended to support the IT infrastructure, versus the power that actually runs the racks, servers, network equipment and other essential components of the datacentre. A PUE rating of 1.1 means that only 10 percent of the total facility's power goes on the support infrastructure, with the rest going on the equipment.

Image: Sam Shead

Datacentre security is vital: there are biometric readers and secure mantraps (pictured) on both levels of the datacentre that control access to the datahalls and are programmed so that the first set of doors must close before the second set opens. Each door has a proximity card reader that is pre-programmed with a client's access information. 

To prevent unwanted guests from accessing the facility, there is a 3m high fence and a gate that is manned by security 24/7. If somebody were to penetrate the fence, they'd have a tough time evading the intruder alarms around the complex, and 50 infrared CCTV cameras.

These security features help make Virtus into a Tier III. Another thing clients look for in a datacentre is increased resilience so they can be confident their services will be available all the time. 

"The reason people go for Tier III is twofold. One is because there is a  level of redundancy built in so there can be some failure and the service will continue," David Watkins, Virtus operations director, told ZDNet. "More importantly, Tier III gives you the ability to concurrently maintain equipment."

The Enfield site fits into the Tier III category because it abides by the "n+1 rule", which means that there is always one spare piece of equipment, be it a generator or an air=conditioning unit, to provide back up in the case of a failure.

For example, the Tier III Enfield site needs two generators to function but there are three just in case one fails. Meanwhile, a Tier IV would need a complete spare set.  

Watkins explained that it would have cost Virtus an extra £15m to make the site Tier IV and would have involved adding large quantities of extra equipment.

Image: Sam Shead

The heat-generating servers are kept at the right temperature by pumping cool air up into the 'cold aisles' that they sit either side of. 

"There's a fan like you have on a PC that pulls the hot air out the back of the server while pulling the cold air in through the front to keep the server cool," said Watkins.

The hot air is extruded out of the back and rises towards the ceiling by convection. It eventually gets sucked back into one of the air conditioning units and is transported to the large cooling units outside the warehouse where it is cooled down again. 

Again, the sites has 'N+1' cooling units, so there are four but only three are needed at any one time for operation.

When Enfield air temperatures are below a certain threshold the pumps will use the water's natural temperature to avoid expending unnecessary energy.

Image: Sam Shead

The datacentre has diverse fibre and power supplies which enter the building at opposite ends, and enable the facility to continue operating as normal even if one of the feeds experiences problems. 

The power supply consists of two 8MW 11KV feeds from the National Grid but Watkins said that the site will never use the full 8MW. He claimed that the site is currently drawing on less than 20 percent of that. 

Nonetheless, datacentres are power-hungry environments and all that power doesn't come cheap. Ultimately, the amount of energy used is determined not by Virtus but by the clients inside the datacentre. 

"The energy bill depends upon the amount of power that tenants draw, which we can't control," said Watkins. 

When operating at full capacity, the site will draw 8MW of power per hour, which is equivalent to 27,000 houses.

Image: Sam Shead

These lithium batteries are in fact a Tier IV feature and are included within the datacentre just in case, on the extremely rare occasion, both of the National Grid feeds fail. 

"The batteries offer uninterrupted power supply," said Watkins. "If there's a power failure, the batteries have enough stored charge to take the IT load while the generator is warmed up."

Image: Sam Shead