Not so long ago, the 19in cabinet that is found in virtually every data centre was a relatively straightforward piece of steel that simply housed equipment. Not any more. Today’s data centre cabinets play a key role in achieving critical requirements such as cooling, equipment density, monitoring and security. It means making the right choice of cabinet has become extremely important, as Matt Goulding, managing director of Cannon Technologies, explains.
Why has this happened? Largely, because of the huge increase in demand for online information and transactional services. From an era when most information was text, we have reached the point where streamed video and increasingly high definition, is needed for almost everything from websites to on-demand TV and video telephony. The latest drivers of this revolution are ubiquitous mobile devices like tablet computers and the iPhone and its competitors.
Developments like this have massively increased the need for data storage, greater bandwidth, and processing capability. This has not only led to the building of new data centres, but also forced companies to pack the maximum possible amount of equipment into their existing physical spaces.
In practice, this has led to the once standard multi-U servers being replaced by 1U pizza-box servers, now the norm. But already, these are being replaced by power hungry blade servers, which can provide an effective density of many servers per U. (A ‘U’ is the height increment between the pairs of mounting holes in a cabinet and typically there are 42 to 52 ‘U’ per cabinet.)
Underlying these moves are the key aims of minimising capital and operating expenditure and maximising return on investment, revenues and growth. But equally, companies want to eliminate unpredictability while also lowering energy consumption and minimising carbon footprint.
A decade ago, power dissipation was no great problem, with ordinary convection being sufficient to remove heat. Now, maximising processing capability and storage within the available space has hugely increased heat density, rising from less than 1kW per rack to of 2-5kW, with high end equipment reaching 20kW or even 30kW.
It means various methods are needed to remove heat from cabinets, and to manage heat generated by the whole data centre, so planners need expert help.
For the individual cabinet, heat is typically extracted by front-to-back airflow, through mesh doors. Cooled air from the computer room air cooling (CRAC) units is fed into the cold aisle and then out into the hot aisle. From there, hot air eventually travels back to the CRAC units for further cooling. If heat density rises above a certain point, it may be necessary to add fans to the rack’s rear door.
Even this technique may prove inadequate, when racks reach an average of 5kW. Then, more sophisticated processes are needed, such as an arrangement called aisle cocooning. As heat density goes on rising, it may be necessary to implement ‘close coupled’ cooling, in which cooling units are mounted directly inside the cocoon, either between cabinets in the row or even within cabinets.
Inside the cabinet
Inside the cabinet, it is vital to control airflow so that back-to-front (hot side to cold side) airflows are eliminated. This kind of air-feedback can degrade cooling performance, causing dangerously high temperatures within the rack, risking device failure. That is why users should install cabinets in which cooling can be upgraded throughout a data centre’s lifetime.
Equipment is already available that takes power dissipation to 30kW or even 60kW per cabinet. Such systems will soon be widely used, and the industry will probably need to create even more powerful cooling solutions in future.
Another problem for data centre managers is controlling access to the extremely important and expensive equipment they contain. Whether the data centre is a single operator location, such as a corporate data centre, or a multi-operator like a co-location data centre, lots of people may need access to each cabinet. Inevitably, not everyone is as careful as they should be, and in some cases damage may even be deliberate.
This means the simple security processes of yesterday like passive key operated cabinet locks, or even code operated, are not good enough. Now, locks must be software controlled, with code, iris or thumbprint recognition required. Nor is it just a matter of controlling who can access the cabinet. It can be just as important to restrict the access time allowed, with alarms generated if unauthorised access is attempted, or when a cabinet is left open beyond an individual’s specified time slot.
Today’s cabinet security systems can be backed up by CCTV cameras that record the access operation. Also, it is possible to specify that two people, such as the technician and a security overseer, must authenticate the system before the cabinet can be unlocked. And as further backup, a complete audit trail, containing video if recorded, can be retained for any possible investigation.
Given the problems posed by ever increasing heat generation, monitoring temperatures inside cabinets sounds like an obviously good idea, yet for a long time it stayed just that – an idea. But times have changed, and today it really is vital, and at multiple points on the cabinet.
The fact is, today’s server-grade processors consume such a level of power, if the cooling becomes inadequate, temperatures will accelerate rapidly and vital chips will die, causing damaging downtime. Even if immediate failure does not occur, regular rises in temperature can seriously shorten the life expectancy of many devices, making potential down-time more likely.
Temperature monitoring is not just a matter of looking at the whole cabinet, it is vital to check it on a per-equipment basis. That is because it makes it possible to find hotspots and do something about them before they become serious, as well as enabling users to install new equipment and know they are not inadvertently creating hotspots. Other benefits include ensuring that a cabinet’s power supplies are not overloaded, and detecting abnormal power loads that could be the sign of equipment developing a fault, thus avoiding future failure.
All of the above explain why power-measuring distribution strips, and the intelligence to analyse their measurements in real time, are so valuable.
As the above shows, today’s data centre is absolutely dependent on the sophistication of the cabinet/rack and the extended infrastructure attached to it. Compared with the past, it represents a huge increase in functional capability. As a result, the task of managing such advanced elements – which could number hundreds or even thousands of cabinets – becomes a major challenge in itself.
The result is, it demands a dedicated tool, such as Cannon’s DCM data centre management software, that can handle all of the inputs and outputs, operating local alarms and controls, and integrating all of these into a data centre’s main network operations centre software platform.
Software control is now a key feature of data centre cabinets, which brings other benefits, like the ability to carry out capacity planning, perform ‘what-if?’ modelling, and do task-management to optimise the deployment of a data centre’s most important resource – its people.
The crucial role data centre cabinets now play makes selecting the appropriate cabinets critical – your data centre’s performance and profits depend on getting that choice right.