Modern companies use computers in almost all aspects of doing business—communication, information storage, accounting, and day-to-day business functions. A data center is a centralized physical facility where corporate computers, network, storage, and other IT equipment that support business operations live. The computers in a data center contain or facilitate business-critical applications, services, and data.

Data centers come in all sizes—they may fill a closet, a dedicated room, or a warehouse. Some businesses with a large amount of IT equipment in their data centers may require more than one data center facility. Companies can also choose to rent server space and have someone else maintain their data center.

A data center might extend outside of a physical facility by using a private or public cloud to augment its operations or storage. A virtualized data center can use servers in remote locations when needed to run larger workloads.

Because data centers contain so much expensive IT equipment, they have special requirements for security and power.

• Abundant, reliable power: The equipment in a data center often requires a large amount of power, from a source that is immune to interruptions through immediately available back-up power. Virtualized or software-defined data centers are more efficient and require much less power than traditional data centers.
• Cool conditions: All of the power and equipment in a data center generate a lot of heat, so data centers often require some kind of cooling equipment to operate optimally. Water can destroy computers, so sprinklers cannot be used to protect the equipment in a data center from fire. Instead, data centers can use chemical fire-retardant systems that smother flames without harming electronic equipment.
• Physical and virtual security measures: Security is an important aspect of any data center because of the business-critical applications and information it contains. A breach where sensitive customer or company data becomes exposed can cost hundreds of thousands of dollars and, in worst-case scenarios, destroy a company’s brand and business. Both physical and virtual security measures are necessary to ensure that a data center stays secure and that businesses are not vulnerable to a data breach. A data center must be protected from theft with physical security measures such as locks, video surveillance, and restricted access. Network and application security software can provide essential virtual security measures.

Data centers can have different levels of security, latency, and resiliency—these levels are known as tiers. Tiered data centers allow for hierarchical data storage, where the files and data for applications that users access most frequently, or that require very high performance, can live in one tier, while data that is not accessed as frequently can live in a different tier. In public cloud-based storage-as-a-service models, tiers with low latency are generally more expensive than tiers with higher latency.

The tier with the lowest latency and the fastest access typically lives closest to the users, where users can easily interact with it on a daily basis. The fastest tier is known as Tier Zero. Businesses such as financial services or medical research that use high-performance computing for big data analytics are frequent users of Tier Zero storage. Lower performing storage tiers can act as back-up for the primary tier, or as storage for data that is less frequently accessed. Archived data can live in the lowest and least expensive storage tier, where high latency is less of an issue.