Physical layout of Data Center
A data center can occupy one room of a building, one or more floors, or an entire building. Most of the equipment is often in the form of servers racked up into 19 inch rack cabinets, which are usually placed in single rows forming corridors between them. Servers differ greatly in size from 1U servers to huge storage silos which occupy many tiles on the floor. This allows people access to the front and rear of each cabinet. Some equipment such as mainframe computers and storage devices are often as big as the racks themselves, and are placed alongside them.
1U represents one rack unit of space. A Rack Unit is 1.75 inches in height (44.49 mm). The sizes are believed to have been derived from telecommunication equipment used in the second world war.
The physical environment of the data center is usually under strict control:
- Air conditioning is used to keep the room cool, it may also used for humidity control. Generally, temperature is kept around 20-22 degrees Celsius (about 68-72 degrees Fahrenheit). The primary goal of data center air conditioning systems is to keep the server components at the board level within the manufacturers specified temperature/humidity range. This is crucial since electronic equipment in a confined space generates much excess heat, and tends to malfunction if not adequately cooled. Air conditioning systems also help keep humidity within acceptable parameters. The humidity parameters are kept between 35% and 65 % Relative Humidity. Too much humidity and water may begin to condense on internal components; too little and static electricity may damage components.
- Backup power is catered for via one or more uninterruptible power supplies and/or diesel generators.
- To prevent single points of failure, all elements of the electrical systems, including backup system, are typically fully duplicated, and critical servers are connected to both the "A-side" and "B-side" power feeds.
- Data centers typically have raised flooring made up of 60 cm (2 ft) removable square tiles. These provide a plenum for air to circulate below the floor, as part of the air conditioning system, as well as providing space for power cabling. Data cabling is typically routed through overhead cable trays in modern data centers. Smaller/less expensive data centers without raised flooring may use anti-static tiles for a flooring surface.
- Data centers often have elaborate fire prevention and fire extinguishing systems. Modern data centers tend to have two kinds of fire alarm systems; a first system designed to spot the slightest sign of particles being given off by hot components, so a potential fire can be investigated and extinguished locally before it takes hold (sometimes, just by turning smoldering equipment off), and a second system designed to take full-scale action if the fire takes hold. Fire prevention and detection systems are also typically zoned, and high-quality fire-doors and other physical fire-breaks used, so that even if a fire does break out it can be contained and extinguished within a small part of the facility.
- Using conventional water sprinkler systems on operational electrical equipment can do just as much damage as a fire. Originally Halon gas, a halogenated organic compound that chemically stops combustion, was used to extinguish flames. However, the use of Halon has been banned by the Montreal Protocol because of the danger Halon poses the ozone layer. Unlike fire extinguishing agents that displace oxygen, Halon did not pose a great risk to people caught in the data center when it was discharged. More environmentally-friendly alternatives include Argonite and FM-200, and even systems based on mists of tiny particles of ultra-pure water.
- Physical security also plays a large role with data centers. Physical access to the site is usually restricted to selected personnel. Video camera surveillance and permanent security guards are almost always present if the data center is large or contains sensitive information on any of the systems within.
What is Data Center