The crucial role of fire systems in data centres
Our insatiable thirst for online storage and bandwidth, driven by the growth of eCommerce and Cloud computing, means demand for data centres has never been higher. These cathedrals of technology are becoming larger and more complex every year and, with 33% off all unplanned outages caused by thermal issues, the challenge is to keep this critical infrastructure running, as fire incidents or even false alarms can have far-reaching consequences.
On 12th September 2016, a gas-based fire suppression system was mistakenly discharged at the data centre of ING, the Dutch banking giant. The ensuing emergency shutdown denied customers access to their money for almost 24 hours and caused widespread inconvenience. While the alert was thankfully false, the incident demonstrates then implications of a data centre fire and perhaps more significantly the vital importance of reliable fire systems, that can also reliably discriminate false alarms.
Causes of data centre fires are diverse, ranging from squirrels biting through wires (Yahoo, Santa Clara, 2012) to lightning strikes (Microsoft, Dublin, 2011). In 2008, an HSBC data centre in Welwyn Garden City in the UK was severely damaged by exploding gas canisters belonging to a building contractor. However, the main causes are overheating and electrical faults, and specialised fire systems both detection and alarm and suppression control are needed to protect this vital infrastructure.
Building a data centre in any environment can cost millions, and the information it contains can be even more valuable, so the provision of adequate fire protection and extinguishant systems is vital. These systems, both active and passive, need to protect the servers, the data and the people who manage them. To function effectively, their design and specification should be based on stringent risk assessments.
An effective fire system should be designed into the building at an early stage, along with all the necessary extinguishant pipework, suppressant storage, and passive fire containment systems. Despite the complications, data centre design offers certain advantages to the specification of a fire system. With no need for public access, there is more flexibility than in other sites, with components such as exposed cables or cable trays less likely to be an issue.
The fire panel
Modern analogue addressable fire panels, like Advanced’s, lie at the heart of the active protection system, working with intelligent detectors to monitor for a whole range of fire types. They can tell how fast a fire is spreading, and alert people by voice, light or sound, using multiple tones and frequencies. Evacuation can be phased to get people out of the building, even in a dynamic fire situation, and the panel can also radically reduce false alarms. Smoke spread in the building can be managed, fires contained, doors opened and closed, suppressants released, the fire service called and CCTV trained on the area in fire. Modern systems can also link to graphical control stations, building management systems and be monitored and controlled over the internet.
The fire system can be single or multi-loop, standalone or networked. In a complex data centre, the installation costs are likely to dwarf equipment prices, but if an unreliable or unsuitable system is installed, the downstream costs may be significant. Advanced’s expertise with data centres is based on a history of complex installations, optimised for performance, quality and ease-of-use, including the £20m West Cambridge Data Centre, part of Cambridge University.
Fire happens fast, so seconds matter. The greater the rate of spread of the fire, the more serious the data loss or downtime can be, so even the best fire system is no good if things can’t happen quickly. Therefore, networking and loop communications protocols that work efficiently are vital and should be key specification requirements, especially on bigger sites where the network will be doing more with more devices, inputs or outputs.
While the server rooms are the primary focus, the building is also likely to contain offices, service areas, staff rooms and other spaces. In many buildings, a smaller server room or larger data centre may very well be part of a much larger office or manufacturing environment. At the other end of the scale, dedicated data centres can be vast and can sometimes be in remote locations, where immediate fire service assistance cannot be guaranteed. The choice of active fire protection system is even more critical in such circumstances.
There are two common approaches to general fire alarm protection and specialist extinguishant release in data centres. The first is the use of integrated extinguishing modules on addressable fire alarm panels. The second is an entirely separate (and perhaps monitored) extinguishant release or suppression control system.
Whatever route is taken, the performance of the installed fire systems should be considered at specification stage. Panels and systems that are EN54-13 compliant, such as the Advanced Axis EN addressable fire system and ExGo suppression control panel, will continually check the condition of their networks, components and wiring, ensuring that they will work when required in an emergency. Many systems also offer redundancy, switching to an alternative processor, or a complete panel if a problem is detected.
Reliability and resilience are essential requirements in data centres, so a fire system that offers immunity from false alarms, combined with rapid detection and extinguishing of real fire incidents, is the ultimate goal.
Data centres will use a range of detector types with a focus on early and accurate smoke detection. The choices made may combine point detectors, using optical and heat detection, with very early warning aspirating smoke detection systems.
Aspirating systems are one of the fastest growing detector solutions, and are ideal for data centre environments. They continuously sample the air in a building space by drawing it in through an array of pipes with small holes at specified points, passing this air over a sensitive detector at a remote location. Some systems can identify precisely where the smoke entered the pipe network. They also offer accessibility and maintenance benefits as the pipes can be installed in hard to access spaces, even directly through the server racks, and there is only one detector to test and maintain. There are several solutions available, and all will offer distinct advantages.
Once a fire is detected it’s important to safely evacuate the building and manage the spread or suppression of the fire.
Although the number of people working in the data centre itself is likely to be less than a typical office, the priority is to alert and evacuate people as rapidly as possible. In the server rooms, where noise levels are likely to be high, EN54-23 compliant or similar visual alarm devices (VADs) should be used, usually in the form of a strobe unit.
Any shutdown and evacuation can be very costly, so it is also important to minimise false alarm incidents. There are several verification and investigation delay solutions available that will significantly reduce false alarms, both before and after a fire signal has been latched on by the panel. Getting information to responsible staff when a signal occurs, or in some cases before a detector has reached threshold, can save valuable time and money. This can be achieved using integrated fire paging systems that will pass detailed fire systems status information to relevant staff.
Direct confirmation of the fire incident is preferable, if not essential, because there are so many factors at work within a data centre, from the heat generated by the equipment to the high airflow within the server rooms. A false alarm can have far-reaching consequences and the primary goal, once an incident is validated and personnel have been safely evacuated, is to keep the servers online. Where a shutdown does occur, it should ideally be only for a short time, covering the lowest possible number of storage units.
Staff training is vital to the successful operation of fire systems and should be factored in from the beginning, with suitable courses for new personnel and regular updates for their colleagues, plus fire drills covering multiple emergency scenarios.
Many data centres will use an addressable fire system for general detection and alarm, with a dedicated or integrated extinguishant release system alongside, such as Advanced’s ExGo.
Suppression systems also come in a wide range of configuration options from networked and interlinked systems to completely standalone. The selection of a solution will depend on budget and performance required. Extinguishing systems are often designed around flooding and detection zones. Detection zones are used to ensure signals are valid, and double-knock signal confirmation is very common, using two detection circuits or zones to confirm a signal on multiple detectors at once before indicating a fire or a release.
A flooding zone is the building area in which suppressant is released and, given the costs of suppressants and the effect a release can have on wider operations, it is often desirable to only release as much gas as required, either from separate gas arrays or a managed central resource.
Extinguishant panels can use pre-programmed parameters (for example a countdown timer) to flood a zone automatically once a fire is confirmed and the timer has elapsed. The timer can offer valuable time to evacuate staff from the flooding zone or cancel release, if the issue has been dealt with or found to be false.
Most extinguishant panels will be in manual operating mode when people are on-site but can be switched to auto to cover all eventualities. Most systems will also have a range of repeaters so that the system status can be seen inside and outside a protected area, and hold and abort buttons that allow the gas release to be paused or cancelled on visual confirmation of the area. This can be important in protecting staff as much as avoiding unwanted suppressant release.
Air conditioning systems play an important part in data centre operations. Keeping server racks well ventilated is a core requirement, but on activation of a suppression system the HVAC must also be deactivated and all doors and dampers closed. If this is not done, the suppressant can be expelled into the outside air as fast as it is pumped into the affected space, drastically reducing its effectiveness. This process can be integrated into some fire alarm systems or can be managed by a third-party system.
A new solution that is available for some sites is to reduce the level of oxygen in the protected area to a level that is safe for humans but inhibits flame ignition, making a fire impossible. While this is an elegant solution, however, the investment in controls and infrastructure can be significant.
Smoke kills, but can also presents other problems in data centre environments. Figures released by the US Federal Commission on Communications (FCC) suggest that 95 percent of the damage in a typical data centre fire is not caused by the fire itself but by smoke from PVC and digital circuit boards, which has a highly corrosive effect on electronic systems in the vicinity. The containment of smoke and smoke extraction are vitally important, and the HVAC or a dedicated smoke control system can be used to accomplish this, in some cases under the automatic or manual control of the fire system.
Smoke must also be removed from an area before inspection following an incident, and the time to get a data centre back in operation following an incident is often a critical requirement.
In summary, there is no standard fire solution for a data centre. As these facilities become larger and even more complex, the risk of fires will increase, and fire systems need to be designed into them from the earliest stages. Specifiers and users need to understand the pros and cons of the solutions available and, importantly, how the fire systems themselves can help deal with the unique challenges presented by data centre installations.
For more information, go to www.advancedco.com