Buying a Server Rack for Your IT Installation

A server rack or data cabinet is commonly used to house IT equipment in a computer room, server room or data centre, or wherever multiple electronic devices are to be used. Each should have a standard 19inch rackmount format but shelves can be installed for smaller width devices. This guide provides a general overview on what to consider and some top tips when buying a server rack.

Server Rack Design

A serve rack is built around four vertical struts or posts (one in each corner) which form a frame, sometimes referred to as an open frame. To the struts, side panels, doors and tops are bolted to form a cabinet.

The width between the vertical struts is 19inches (483mm) and this a standard measurement for a serve rack. Any equipment that is 19inch rack mountable, can be installed into a server rack. The equipment will be attached to the front and possibly rears stuts using M6 cage nuts and bolts and placed on slide-rails or a suitable shelf within the server cabinet.

The vertical height of the server rack is measured in standardised units, with the smallest being 1U = 1.75inches or 44.45mm. The U-heights are marked on the vertical struts and cabinet sizes range from 1U to 47U.

10 Points to Consider When Buying a Server Rack

This list of 10 key points has been put together after guiding clients to the right server rack for their application.

1. Cabinet Depth: server racks have a defined depth and for data cabinets this can be 600 to 800mm or for server racks 900 to 1200mm deep. This is the maximum outer depth of the cabinet, but the internal depth will be shorter than these. It is important to select a cabinet that has a suitable maximum internal depth for the equipment to be installed. The most popular depths for serve room and data centre installations is 800-1000mm deep. A 1000mm deep cabinet has a maximum internal depth of 870mm, suitable for most IT servers. Other equipment to consider can include switches, routers, HMI monitors, KVM switches, PDUs, uninterruptible power supplies, environmental monitoring devices and rackmount fire suppression systems. Tip: the depth of your devices can typically be taken from datasheets or measured but remember to add 100-150mm for power cords and network cables.
2. Equipment Height: each of your rackmount devices should have a U-height. Add these up to get a total U-height required for the data cabinet or server rack. Where your devices do not have a published U-height, measure their height, and divide by 44.45mm to work out the height required. Shelving units can then be purchased to place these devices onto. Tip: add 1U per shelf and remember to purchase sufficient M6 cage nuts and bolts to install the shelves and equipment into the server rack. See our rack size guide for a list of typical rack sizes.
3. Choose a Width: the standard width is 600mm. An 800mm width cabinet may be available and the wider cabinet allows room for side cable management. Top tip: consider doorways and installation room when selecting a cabinet width as an 800mm cabinet will not go through a single-leaf doorway.
4. Door Choices: there are two doors on a server cabinet, front and rear and they should be fitted and closed when access is not required. This is a security measure (as they can be locked – key or combination lock or RFID access controlled), and also aids air flow management. Typical front door choices include bronzed glass, perforated or mesh metal. Read doors are either solid, perforated or mesh. Tip: bronzed glass or mesh front doors are popular, with rear mesh doors to aid air flow.
5. Paint Colour: most rack suppliers offer a choice between standard black (Black RAL9005) or grey (Grey BSI BS4800). Other colour choices can include white or colours on demand. It can be costly request a non-standard paint colour. This is because of the cost to clean and prepare the paint machinery and to be economically viable, the paint run has to cover a large number of cabinets, frames and shelves. Tip: stick with the standard colour range if you only need a one or a small quantity of cabinets.
6. Fully Built or Flat Packed: server cabinets can be supplied fully assembled or as flat packs that can be built onsite. Flatpacks can take time to assemble but provide a convenient way to overcome onsite logistics issues. Top tip: make sure if you go for a flat pack that there is sufficient room inside or close to the final installation appoint for assembly. The larger the cabinet, the more room and assistance will be required to build the cabinet.
7. Power Distribution: all the devices within cabinet will require powering. Most loads are AC powered but you could in exceptional circumstances have DC loads. The most common method for powering equipment in a rack is via a power distribution unit (PDU). Tip: make a list of all the loads to be powered, their size (VA, Amps or Watts) and socket connection requirements; then select a suitable PDU (horizontal or vertically mounted) and if required purchase longer load power cords which can be important in very tall cabinets.
8. Fan Cooling and Air Flow Management: additional cooling can be purchased to help extract heat from the server cabinet. Fan trays and roof mounted fan assemblies can be used or a complete air-conditioned server cabinet. Tip: having doors closed and side panels improves the air flow through a cabinet. Blanking panels should be used where there are unfilled spaces at the front of the server rack.
9. UPS Backup Power:critical loads in the server cabinet should be protected by an uninterruptible power supply. Then PDU will connect directly to this or a UPS maintenance bypass arrangement. The UPS may be rack mounted or sit outside the server cabinets.
10. Environmental Monitoring: all electronic equipment generates heat and server rooms and data centres rely on local air conditioning systems to maintain a suitable room ambient of 18-27°C. Hot spots can be build within a server cabinet due to poor airflow management and failure of the air conditioning system can lead to a fast build-up of heat and to high levels that can present a fire risk. Install a suitable environmental monitoring unit to provide automatic alerts (email and SMS text) should temperature or humidity levels rise above pre-set levels. Tip: most environmental monitoring devices can connect several sensors and consideration could be given to monitoring for water leakage, room entry, server cabinet door access, smoke detectors and third-party systems to provide a comprehensive overview.

Another issue to consider is noise output. This is important for sites without a computer or server room, where the rack has to be placed close to where people work. IT servers generate noise, on start-up and when under load, and an acoustic server rack can reduce the noise output by up to 95%. Most server racks will have bottom cable access. Top down may be an option where this is required by the site; normally where there is no raised access floor.

Summary

This guide to buying a server rack or data cabinet is intended for installations of 1-5 cabinets, where it may be less important to consider hot and cold-aisle POD arrangements. The selection and buying process is relatively straight forward when a step-by-step approach is followed, and a typical server rack will give years of service. Our projects team is always on hand to answer questions and guide you through the process, and even provide on-site placement and flatpack assembly.