A data center is a facility used to house computer systems and associated components, such as telecommunications and storage systems. It generally includes redundant or backup power supplies, redundant data communications connections, environmental controls (e.g., air conditioning, fire suppression), and special security devices. Today, data center provider classifications are typically rated as the following:

• Tier 1 data center service providers
  Are basic computer rooms with limited redundancy. Require a full shut down for preventative maintenance. These types of data centers are susceptible to disruption from both planned and unplanned activities. Annual tier 1 data center service downtime is approximately 28 hours.
• Tier 2 data center service providers
  Have redundant and some single non-redundant distribution paths serving the site’s computer gear. Tier 2 data center service data centers are susceptible to disruption from both planned and unplanned activities. Annual tier 2 data center service providers downtime is approximately 22 hours.
• Tier 3 data center service providers
  Have sufficient redundancy in place for planned and unplanned events. Operation error or spontaneous issues may cause some data center disruption. Annual tier 3 data center service providers downtime is approximately 2 hours.
  
• Tier 4 data center service providers
  Are the most redundant data center available today. Redundant capacity systems and multiple distribution paths serving the computer equipment. Annual tier 4 data center service downtime is less than 1 hour.