What was once considered a straightforward steel structure now plays a critical role in ensuring the smooth operation of today’s data centres. As cabinets continue to evolve Mark Hirst, T4 product manager at Cannon Technologies, explains why failing to give these products the respect they deserve could prove costly.

Back in the early days of the data centre industry, cabinets were simply a ‘one size fits all’ location for servers and other equipment. As the sector has grown to meet the demands for greater data storage, bandwidth and processing power, cabinet specification has become a fine art that requires a serious amount of consideration.

Sizing it up

It’s still surprising just how little attention is paid to choosing the right sized cabinet for the job and this is one of the most common pitfalls to avoid. Put simply, the required size of the cabinet directly relates to the type of equipment to be installed.

In the vast majority of cases a 600mm deep cabinet is not going to suffice and even a depth of 800mm is unlikely to offer enough space to house today’s high density servers. Selecting a 1000mm or 1200mm version is therefore advisable, as it is always recommended to have some space between the back of the server and the rear door. Also, it pays to select cabinets with adjustable mounting posts, as this will allow universal server mounting and add a valuable level of flexibility to an installation.

Put simply, it is always better to over-specify than under-specify, as any extra space will almost certainly be utilised by the next generation of server technology, therefore giving an extra level of future proofing to the installation while increasing return on investment (ROI).

Power factor

Power distribution units (PDUs) are a ubiquitous part of any cabinet installation and the total energy demand required per unit has risen dramatically over the past 15 years, from an average power density of 1-2kW to an average of 4-6kW per cabinet.

Therefore, making sure that there is enough room allocated to house them is imperative – anyone trying to fit a 30 socket vertical PDU in a 32U cabinet will soon run into problems.

According to the Uptime Institute, human error causes around 70% of the problems that plague data centres. Therefore, using PDUs with lockable sockets is a great way to avoid any accidents. Also, when it comes to using intelligent PDUs (iPDUs), be careful about assigning IP addresses to each, as the cost of doing so can soon mount up.

Cost cutter

Many of the issues surrounding cabinet specification can be put down to one thing – cost. However, going for the cheaper option can prove to be a false economy, as they do not usually have the same user-friendly design features that are found in high-end products.

For instance, if a cabinet has a solid steel roof it could need holes cutting into it to feed cables through. Doing so can create sharp edges, which can, in turn, cause damage to the cabling and be a health and safety hazard.

It makes far more sense to look at what needs to be achieved and purchase the right cabinet to match. For instance, it might be more appropriate to have brush strips at the top and base and have factory made holes in which to allow cables to go from front to back, or into the centre and up and down. The most important issue with patching is maintaining the bend radius of the cable, something that a cabinet with enough room and in-built flexibility will be able to facilitate.

Climate control

The DatacenterDynamics 2012 Global Census found that the number of high-density cabinets – those over 10kW per cabinet – as a proportion of total cabinets increased from 15% in 2011 to 18% in 2012. That’s a lot of power.

It is widely acknowledged that a 10°C (50°F) rise above room temperature could result in a 50% reduction of the mean time between failure (MTBF). A cabinet plays a vital role in maintaining the integrity of a cooling system and by controlling the air temperature server components at the board level are kept within a manufacturer's specified temperature and/or humidity range.

Basic heat extraction uses front to back airflow, through mesh doors, from the cold aisle out into the hot aisle, from where the hot air finds its way eventually back to the computer room air conditioning (CRAC) units for cooling. There comes a point, however, where this configuration cannot cope because much of the hot air out of the rear finds its way into the cold aisle, warming up the cold air before it gets chance to enter the cabinets.

Coping mechanism

As the name suggests, cold aisle containment encloses the cold aisle and prevents the mixing of cold air and hot exhaust air. State-of-the-art aisle cocooning systems enclose the space between two facing rows of cabinets, sealing the airspace between them with a low-level ceiling and access controlled corridor door(s). Again, it is important to make sure that a cabinet is suitable for use with a chosen cooling system.

It is also advisable to fit sensors that can detect changes to the microclimates inside cabinets. According to guidelines by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), temperature sensors should be placed on the cool air inlet side of a cabinet near the bottom, top and at the centre. They will then indicate the temperature of the air being drawn in to cool the IT equipment, and the higher the data centre set point the less energy is consumed. According to ASHRAE, the inlet temperature can safely be as high as 27C (80F).

Panel decision

Also on the subject of temperature control, it is worth remembering that traditional cabinet designs utilise totally detachable side panels for maintenance or moves, adds and changes (MACs). However, panels that are removed for even the shortest period of time can totally spoil cold air/hot air separation and negate the benefits of an aisle cocooning system.

Therefore using a unit that has sliding partition panels for cabinets bayed in rows is recommended, such as Cannon Technologies’ Smart Space cabinet, which offers narrow partition and full depth panels.

Used in pairs the narrow partition panels can slide backwards and forwards to open cross cabling apertures between adjacent cabinets, or completely close off inter-cabinet access providing a highly secure solution. Either way, cooling efficiency is maximised without compromising access and they can be removed or added to bayed cabinets during the entire lifecycle of the installation.

Blankety blank

Cabinets with raised feet for levelling can create a backwash of air underneath them, while there may be gaps either down the sides or where there is missing equipment. Although blanking plates should be used to cover these as part of any best practice policy, they are often forgotten about, leading to a mix of hot and cold air.

This is a continual source of frustration to those of us who are concerned with maximising the energy efficiency of data centres, and blanking plates are the lowest cost way to save a fortune. Therefore, avoid the pitfall of spending money on cooling systems without taking care of the basics first.

Blanking panels, should be sized to fit the required amount of unused cabinet space, there are a variety of quick fit blank panels with no tools required to fit them. Other flat and angled blank filler panels in several cabinet unit sizes are available, including brush guard panels that allow cables to pass through, whilst still providing thermal protection to maintain isolation.

Security guard

An integrated security approach to cabinet specification is hugely important and, as a growing number of organisations are finding out, not only must they secure these particular infrastructure components, they must also be able to prove the efficacy of their auditing systems to one or more governance bodies.

Modern locking systems such as swinghandles are highly secure, robust, ergonomic, and can be retrofitted. However, to add another layer of protection they can be installed with an electronic keypad that simply screws to the back of the standard swinghandle, converting it into a remote access solution. The tamper proof cabling to the lock itself can also be routed through the internal door skin to hide it from view and further enhance security.

A locking system will usually be used in conjunction with a personal identification number (PIN) or radio frequency identification (RFID) device. When it comes to room, row or cold aisle entry, one reader device may open all the locks in the cabinets in a particular row if required. Another increasingly popular way of ensuring that only authorised personnel have access to cabinets is by using biometric technologies such as automatic fingerprint identification, iris and retina scanning, face recognition and hand geometry.

Lighten up

It is also worth considering that a data centre could save a third of its lighting costs by replacing black cabinets with white or grey versions.

In fact, choosing to use grey or white cabinets during an equipment refresh can make even bigger savings than intelligent lighting systems that use movement sensitive lights. This is a growing trend and HP’s kit is now in grey and Cisco’s new data centre in the USA used bright white cabinets throughout.

Ambient light levels are crucial for the engineers who maintain the systems but it can be the equipment itself that can make a significant impact. The light reflective value (LRV) of black server cabinets can be as little as five per cent whereas grey or white will reflect up to 80 per cent of the light. Using the LRV of the server cabinet colour, it is not unrealistic to see a saving of around 30 per cent on the lighting in a data centre.

Talk time

They key to successful cabinet specification and installation is to be as precise as possible during the planning stage and be realistic about potential levels of growth. One important way to avoid any issues is to talk to leading manufacturers and explain the requirement. They will also be able to anticipate any issues and use their vast experience to help make sure that the right cabinet is selected first time, which will ultimately save valuable time and money.

Editorial contacts
Debby Freeman
+44 (0)1487 843366
debby.freeman@communicator-marketing.co.uk