The Server Rack is a necessary part of the data centre. Whether you have one rack or multiple racks, it's vital to ensure that the racks design and its installation, is done with due diligence, ensuring that not only current requirements are considered, but that future technology upgrading is easy to implement.
When installing racking, the physical location and the installed equipment cabling, power distribution and cooling requirements, should be considered.
Siting the Rack
There should be a systematic plan to determine where server racks need to go in existing or newly designed data centres.
For smaller datarooms, a suitable room will need to be set up. As these rooms will usually contain sensitive data, secure access to the room and the rack is essential. Depending on the size of the installation, the servers will generate a fair amount of heat so you may need to plan for heat extraction, whether that be by extraction fans or ducted air conditioning. Noise generated can be high, so consider reduction by using low noise fans and acoustic shielding of the individual racks, to protect technicians working in the room. The room may also need acoustic shielding to prevent disturbance if the room is near a working office.
Choosing Racks
The choice of server racks is important, as they will house critical and heavy equipment, so the rack will need to be high-quality, robust manufacture to protect the equipment securely. It is advisable to pick a cabinet that allows room for expansion over and above your current needs, as invariably additional requirements will arise sooner rather than later!
The size of the server rack you require depends on how much equipment you need to install plus estimated expansion. Server racks will mainly be floor-standing cabinets, and will come in various U sizes – usually, from 18U to 47U or sometimes higher – (a 24 port patch panel or 24 port switch is usually 1U). They will be available generally in 600mm or 800mm widths. The depths of data cabinets are traditionally 600mm and 800mm – but most server cabinets are 1000 or 1200mm deep to accommodate larger server units. They will have depth-adjustable front and rear 19" rack uprights, allowing various shelving and deep equipment to be supported at both front and rear. Most will have doors on the front and back of the racks to allow easy access for installation and maintenance. Removable side panels are a must to not only allow access but to enable easy baying together of cabinets side by side. These doors and side panels are lockable and upgradeable with high security or alarmed locks, depending on security requirements. The rack doors can be solid steel glass or mesh doors – choice of which depends on whether basic cooling or sealed and extracted air cooling or acoustic reduction is required.
Finally, it is vital to consider how you will get the rack into the building and room – are the doors, lifts or stairwells big enough for the chosen rack to pass? – if not then the solution would be to select the rack in "flat-pack" form to build in situ.
Basic Server Rack Selection
Height of the Server Rack
Server rack and data cabinet heights stated in 'U' sizes. U is a standard height for all rack-mount equipment and equates to 1.75" (44.45mm). A 24 port patch panel or switch, for example, will be 1U in height. U size only refers to internal equipment mounting space – so it's essential to check the external dimensions to ensure you have sufficient clearance height for the cabinet. The total size will be higher to accommodate roof fans, cable entry and feet or castors. For example, a 27U rack will have 1202mm internal rack height, while outside it is likely to be around 300mm extra.
Decide on the equipment you want to mount inside the rack. If any equipment isn't rack-mountable, check its height and divide by 44.45 to give you an approximate U size. This equipment should be sited on a shelf fitted to the 19” uprights, and the shelf will take an additional 1U of space. Once you've sized the server rack, It is advisable to allow, at the very minimum, 10% extra room for future expansion, having to migrate equipment from one server rack to another in the future will cause much disruption and cost.
Width of the Server Rack
Server rack and data cabinet widths are supplied in either 600mm or 800mm widths and contain standard 19" mounting uprights for rack-mount equipment. The advantage of 800mm width is that there is more room each side of the 19" uprights for cable management, compared with 600mm width. If the cabinet is used for patching with a large quantity of copper or fibre patch leads, it is important to have room either side for the patch cords to ensure the neat and easily manageable routing of the patching.
Depth of the Server Rack
Server rack and data cabinet depths were once usually 600mm or 800mm in depth; however, servers are now shorter in height but deeper. A typical rack-mount server may take up only 1u or 2u of space, but 800mm or more in-depth. Cabinets nowadays come in 900mm, 1000mm 1200mm external depths, to accommodate this size of server. As the maximum internal working space is usually 100- 150mm less than this, then an 800mm deep Server will need a 1000mm deep rack to house it. When mounted on the 19" uprights, the server also needs to be supported by the rear uprights. Therefore, server racks will have 19" mounting uprights at the front and back. These are adjustable forward and backwards to position them to mount the server and ensure adequate space to the front and rear for patching and power inputs.
Ventilation of Server Rack
Servers generate heat so will need to be ventilated to prevent malfunction or failure, the cooling airflow is generally drawn through the front and expelled to the rear of the server. Server racks will have the facility to mount fans to the roof to remove this warm air from the cabinet, particularly when there are many servers within the rack. Air intake will usually be via vented mesh doors. However, if there is a requirement to reduce noise from the cabinet, recycle or expel the racks heat, then solid doors will minimise sound or heat loss to the room.
Server Rack Accessories
Server racks come with adjustable jacking feet and removable transport castors ready to use, however, there are optional accessories to meet most requirements, such as:
- Heavy-duty Castors – if the cabinet needs to be movable when loaded.
- Plinth system for the cabinet to sit on and assist with cable entry and stabilising arms prevent possible cabinet toppling when servers are pulled out for maintenance.
- Roof fan units – are mounted in the top aperture taking no space.
- Rack-mount fans – are mounted to the 19" uprights and placed to move air in the required direction.
- Cantilever or modem shelf – mounts to front 19” uprights for light duty.
- Fixed Shelf – mounts to front and rear uprights giving a heavy-duty solution for heavier and deeper equipment.
- Telescopic Shelf – mounts to front and rear uprights allowing pull out access to equipment.
Server Rack Cable Management
Cable management within the rack is essential for tidiness and ease of patching, identification and maintenance so the following accessories should be considered:
- Cable Trays - Mounted on the rack's inside for neatly routing cables vertically.
- Jumper Rings - These mount vertically on the side of the 19” uprights in 800mm wide cabinets typically used to route patch cables within the rack.
- Horizontal Cable Tidy Bars - These mount on the 19" uprights to route patch cables neatly to using patch panels and switches.
- Brush Strip Panels - These mount horizontally on the 19" uprights and used to route patch cords into the cabinet and assist with airflow management.
- Blanking Panels – Mount to 19” uprights and used to cover unused rack space to give a neat appearance, hide unsightly cables or equipment and very useful to manage the airflow around the cabinet.
- Other Equipment
- Servers and other active equipment will require power, so consideration must be given to supply this. A Power Distribution Unit (PDU), connected directly to the incoming power supply or an Uninterruptible Power Supply (UPS) will usually provide this.
The PDU style depends on the number of outlets, type of outlet, surge/filtered version, and whether some monitoring is required. For a comprehensive overview of PDU styles click here.
A UPS will sit between the incoming power and the PDU and is vital if you are running mission-critical operations, as it will maintain power for a short period after power failure until back up kicks in or an orderly shutdown is enacted.
