There once was a time when cabinets were simply viewed as a ‘one size fits all’ location for servers and other equipment. However, as the data centre 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.
There are five key areas to address when specifying data centre enclosures: capacity (size), power allocation, cooling and climate control, access, and security. Let's take a look at each of these in order:
Capacity/size
It’s 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.
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 1,000mm or 1,200mm 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 multi-adjustable mounting posts, as this will allow universal server mounting and add a valuable level of flexibility to an installation.
It makes sense to look at the requirements and purchase the most suitable cabinet to match. For instance, it might be more appropriate to have large apertures with brush strips at the top and base and have cable management 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.
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.
Power allocation
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 or more. Therefore, making sure that there is enough room is imperative – anyone trying to fit a 30 socket vertical PDU in a 32U cabinet will soon run into problems.
In addition, according to the Uptime Institute, human error causes around 70 percent of the problems that plague data centres. Therefore, using PDUs with lockable sockets is a great way to avoid any accidents. Intelligent PDUs allow managers to see power consumption in real time and make informed decisions regarding electrical capacity. Per circuit monitoring would be regarded as entry level by most today and per outlet metering and control is a must for unmanned sites.
Cooling and climate control
Recent research from DCD Intelligence, a division of Datacenter Dynamics, found that the number of high-density cabinets in servers – those over 10kW per cabinet – as a proportion of total cabinets increased by 8.5 percent globally between 2012 and 2013 to 15.2 percent. 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.
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 infrastructure
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. These will indicate the temperature of the air being drawn in to cool the IT equipment, and the higher the data centre cold air set-point the less cooling energy is consumed. According to ASHRAE, the inlet temperature can safely be as high as 27°C.
Access
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.
Using a unit that has sliding partition panels for cabinets bayed in rows is recommended. 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.
Also on this subject, 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. Blanking plates should be used to cover these as part of any best practice policy and 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
Making an aisle work with multiple vendor’s cabinets and cooling systems requires careful design, and consideration may need to be paid to possible ‘day 2’ changes.
Security
Security is hugely important in the data centre and, as a growing number of organisations are finding out, not only must they secure their cabinets, 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, handles can be installed with an electronic keypad and a pack that simply screws to the back of the standard swinghandle, converting it into a remote access system.
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 characteristics.
The key to successful cabinet specification is to be as precise as possible during the planning stage and be realistic about potential levels of growth.
Mark Hirst is with Cannon Technologies