Physical Layout
A data center can occupy one room of a building, one or more floors, or up to the whole building. Most of the equipment is often in the form of 1U servers (so-called "pizza boxes") racked up in 19 inch rack cabinets, which are usually placed in single rows forming corridors between them. 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. The physical environment of the data center is usually under strict control:
- Air conditioning is used to keep the room cool, generally around 17 degrees Celsius (about 63 degrees Fahrenheit). This is crucial since electronic equipment in a confined space generates much excess heat, and tends to malfunction if cooling is not handled.
- Backup power is often available. This can include one or more uninterruptible power supplies and diesel generators located close by.
- 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 2 foot (600mm) 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.
- 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 fires do break out they 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 so using it is not an option - also ordinary water and electricity don't mix well. Originally halon gas was used in the event of a fire to extinguish flames - an inert gas that pushes all the oxygen out of the room. However this has now been banned in some countries because of the danger it poses to people if they are trapped in the same room without emergency breathing oxygen supplies. More recent alternatives include Argonite and FM200, 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.
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Network Infrastructure
Communications in data centers today are most often based on networks running the IP protocol suite. Data centers contain a set of routers and switches that transport traffic between the servers and to the outside world.
Some of the servers at the data center are used for running the basic Internet and intranet services needed by internal users in the organization: email servers, proxy servers, DNS servers, etc.
Network security elements are also usually deployed: firewalls, VPN gateways, Intrusion detection systems, etc. Also common are monitoring systems for the network and some of the applications.
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