How to choose a server rack
Computer room servers, rack mounted equipment and cabinets are an expensive asset that requires careful choice and considerations before purchase. In this article we will look at some of the important factors that need considering when you choose a server rack.
One of the most important things to consider when selecting a cabinet is how it effects the method of cooling you employ. Ensuring airflow and sufficient cooling around rack mounted equipment is critical for reliability. The amount of heat generated in a rack will depend on the density of the equipment installed and can range anything from 4-12kW per hour heat output. This is set to increase as rack density and future equipment is installed. Estimates put the potential at 30-50 kW heat output per rack.
There are two types of rack structure you can purchase. A perforated server rack has perforated holes in its structure. This allows maximum airflow through and around the rack. These racks are ideal in a situation where your primary method of cooling is through air conditioning in the computer room, fans and blowers (ambient air cooling).
Alternatively a fully sealed rack type can be used. This has the opposite theory of operation to the perforated rack. It’s aim is to keep the air inside, and use internal rack cooling system such as a rack air-conditioned or liquid cooling system. The aim here is to keep the cool air inside, and exhaust the heat to the outside of the rack.
Rack air conditioners are not generally used in an integrated data center environment as they already have sufficient centralized air conditioning designed into the building. However in a warehouse, office or small wiring closet environment a rack air conditioner is often the ideal choice for cooling. However it should be ensured that the hot air removed from the cabinet is sufficiently exhausted from the room, especially in confined spaces. The cooling efficiency is improved if the ambient external temperatures are not too high, and this also prevents the rack AC from overheating.
Airflow around the equipment within the rack is also important, as this ensures that heat is removed away from the equipment. Many racks are designed with built in channels for cable management and channels also for improved airflow. In addition to this utilizing 3phase power to the rack increases the available amperage, which reduces the number of heat producing PDU’s needed to power the equipment, and increasing the space available for airflow. Removing unnecessary equipment and creating space for air to move will increase airflow.
Ensure that the rack you purchase has sufficient space for all your equipment, including any future expansion or upgrades. The size of rack equipment is measured in “Unit” sizes, or U’s. A 1U server for example is equal to 1.75” in height, 2U would be double this, 3.5”. The racks internal height is measured from the tallest point of a side rail to the bottom chassis. The depth is measured from the inside of the front and rear doors. Also consider that in addition to the servers you will need to mount backup UPS, LCD screens, network switch/patch panels. Therefore to mount 20 2U servers of 2U each, you would require a minimum of 40U rack height. Add in a 1U patch panel and 2U UPS battery backup and you would ideally want a 44U rack capacity. Oversizing your rack is better than under sizing so that you have less density, room for future expansion and increased capacity for airflow around the rack.
Your rack is an investment, not just financial but also an operational investment. Important information stored on the servers, and systems that it runs can make them critical to your business infrastructure and processes. Physical security threats from sabotage, or damage, needs to be considered. Most racks have a locking mechanism that uses either a key or a smart card (RFID) access card. AKCP’s cabinet controller provides security in this regard, with access control and a camera to monitor and administer who has access to your racks. Together with our Computer Room Management Software AKCPro Server it’s easy monitor your racks and recall access logs synchronized with video surveillance.
It is critical to monitor the performance of your rack, especially the temperature, humidity, power and airflow. As discussed previously temperature and airflow are important considerations when selecting your rack. Equally important is the right monitoring solution to ensure that the rack is performing as expected, and as efficiently as possible. AKCP provides a range of environmental and power monitoring sensors together with Intelligent Base Units. Fully SNMP compliant they can be used with a range of NMS software (whatsup gold, HP Open View, IBM Tivoli etc) or with our own Computer Room Management Software, AKCPro Server that integrates environmental monitoring, video surveillance and access control into a single solution. Protect your investment, and ensure maximum up time of your system with alerts such as SNMP traps, E-mail, SMS and MMS that warn of pending disaster. For more information on computer room environmental monitoring solutions visit the AKCP solutions page.