Data centers are physical or virtual infrastructure commonly run by large companies or government agencies，which typically involve storing, processing and serving large amounts of mission-critical data to clients in a client/server architecture. However, they are also increasingly used to provide a fast-growing cloud solution service for private and business applications.
A data center, or datacenter, often requires extensive redundant or backup power supply systems, periodic backups，cooling systems, redundant networking connections and policy-based security systems for running the enterprise's core applications. So, a data center preferably consists of a well-constructed, sturdy building that houses servers, storage devices, cables, and a connection to the Internet.
The data center is connected to two separate grid sectors operated by the local utility company. If one sector were to fail, then the second one will ensure that power is still supplied.
In addition, the data center has many diesel generators, which are housed in a separate building. Together, they can produce enough output that is sufficient to cover the data center's electricity demand in an emergency. The diesel motors are configured for continuous operations and are always in a preheated state so that they can be started up quickly in the event of an incident. It only takes an outage in just one of the external grid sectors to automatically actuate the generators.
Within the data center, block batteries ensure that all operating applications can run for 15 minutes. This backup system makes it possible to provide power from the time a utility company experiences a total blackout to the time that the diesel generators start up.
The uninterruptible power supply (UPS) also ensures that the quality remains constant. It compensates for voltage and frequency fluctuations and thereby effectively protects sensitive computer electronic components and systems. A redundantly designed power supply system is another feature of the data center. This enables one to perform repairs on one network, for example, without having to turn off servers, databases, or electrical equipment. Several servers or storage units have multiple, redundant power supply units, which transform the supply voltage from the two grid sectors to the operating voltage. This ensures that a failure of one or two power supply units does not cause any problems.
All electronic components and especially the processors generate heat when in operation. If it is not dissipated, the processor's efficiency decreases, in extreme cases, to the point that the component could fail. Therefore, cooling a data center is essential, and because of the concentrated computing power, the costs to do so are considerable.
For this reason, servers are installed in racks, which basically resemble specially standardized shelves. They are laid out so that two rows of racks face each other, thereby creating an aisle from which the front side of the server is accessible. The aisles are covered above and closed off at the ends by doors. Cool air set to a temperature of 24 to 26°C is blown in through holes in the floor, flows through the racks, and dissipates the heat emitted by the servers.
Generally, a server room will contain several such "enclosed" server rows. The warm air from the server room is removed by the air-conditioning system. Yet, even the air-conditioning system has to dissipate the heat. When the outside temperature is below 12 to 13°C, outside air can be used to effectively cool the heat absorbed by the air-conditioning systems.
At higher outside temperatures, the air-conditioning systems are cooled with water, made possible by turbo-cooling units. They are not all used to cool the data center, given that some are used as reserve units. Should a cooling system fail, the time until the backup unit is operational must be covered. To top it off, the turbo-cooling units also have to dissipate heat. There are many heat exchangers on the data center's roof for this purpose, which release hot air into the environment. At outside temperatures above 26°C, the heat exchangers are sprinkled with water in order to make heat dissipation more effective through evaporative cooling. The large amounts of water consumed in the summer are covered by waterworks allocated to the data center. The municipal water supply system provides a reserve supply in this case and acts as a failsafe.
Data Center Tiers
ANSI/TIA-942: Data Center Standards Overview describes the requirements for the data center infrastructure. The simplest is a Tier 1 data center, which is basically a server room, following basic guidelines for the installation of computer systems. The most stringent level is a Tier 4 data center, which is designed to host mission critical computer systems, with fully redundant subsystems and compartmentalized security zones controlled by biometric access controls methods. Another consideration is the placement of the data center in a subterranean context, for data security as well as environmental considerations such as cooling requirements.