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Data Center
Data Center
By LinuxHPC.org and Cluster Resources
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A data center is a facility used to house mission critical computer systems and associated components. It generally includes environmental controls (air conditioning, fire suppression, etc.), redundant/backup power supplies, redundant internet connections and high security.
Descriptions
A data center is a facility used for housing a large amount of electronic equipment, typically computers and communications equipment. As the name implies, a data center is usually maintained by an organization for the purpose of handling the data necessary for its operations. A bank for example may have a data center, where all its customers' account information is maintained and transactions involving this data are carried out. Practically every company that is mid-sized or larger has some kind of data center with the larger companies often having dozens of data centers. Most large cities have many purpose-built data center buildings in secure locations close to telecommunications services. Most colocation centers and Internet peering points are located in these kinds of facilities.
As data is a crucial aspect of most organizational operations, organizations tend to be very protective of their data. A data center must therefore keep high standards for assuring the integrity and functionality of its hosted computer environment. This is depicted in its physical and logical layout.
Before the dot com crash, millions of square meters of general-purpose data centers were built in the hope of filling them with servers for web hosting and application service providers. However this demand never materialized.
Physical layout
A data center can occupy one room of a building, one or more floors, or the whole 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 telecomms equipment 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, generally around 20-22 degrees Celsius (about 68-72 degrees Fahrenheit). More importantly, the primary goal of data center air conditioning systems is to keep the server components at the board level within the manufacturer's specified temperature range. This is crucial since electronic equipment in a confined space generates much excess heat, and tends to malfunction if not adequately cooled.
- 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.
- 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 datacenter 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.
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. Redundancy is sometimes provided by getting the network connections from multiple vendors.
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.
Applications
The main purpose of a data center is running the applications that handle the core business and operational data of the organization. Such systems may be proprietary and developed internally by the organization, or bought from enterprise software vendors. Such common applications are ERP and CRM systems.
Often these applications will be composed of multiple hosts, each running a single component. Common components of such applications are databases, file servers, application servers, middleware and various others.
All text and graphics used in this article is available under the GNU Free Documentation License. It uses material from the Wikipedia article "Data center".