A backup site also called a recovery site or alternate site is a location where an organization can continue operations after a disaster, such as fire, flood, terrorist threat, or other disruptive event. Back up sites are an important part of the organization's disaster recovery plan and overall business continuity planning of an organization.

A backup, or alternate, site can be another data center owned by the same organization or one provided by a disaster recovery company. In some cases, one organization will have an agreement with a second organization to operate a joint backup site. In addition, an organization may have a reciprocal agreement with another organization to set up a site at each of their data centers.

These sites differ in how prepared they are and how quickly they can take over operations. Sites are generally classified based on how prepared they are and the speed with which they can be brought into operation: "cold" (facility is prepared), "warm" (equipment is in place), "hot" (operational data is loaded) –- with increasing cost to implement and maintain with increasing "temperature".

A cold site is operational space with basic facilities like raised floors, air conditioning, power and communication lines etc. Following an incident, equipment is brought in and set up to resume operations. It does not include backed-up copies of data and information from the original location of the organization, nor does it include hardware already set up. The lack of provisioned hardware contributes to the minimal start-up costs of the cold site, but requires additional time following the disaster to have the operation running at a capacity similar to that prior to the disaster. In some cases, a cold site may have equipment available, but it is not operational.

Because cold sites have no pre-installed technology or data, they take the longest to set up after a disaster. However, they are also the least expensive option to maintain, making them popular among smaller businesses or organizations that can tolerate longer downtime.

Some cold sites may have older or spare equipment available, but it is not usually operational until needed. It minimizes ongoing costs, it greatly increases recovery time and the effort needed to resume normal business operations.

A warm site represents a compromise between a cold site and a hot site. These facilities usually have some hardware, software, and connectivity already in place. The systems may not be running in real time, but the basic setup exists. Data backups may be stored on-site or remotely, although they might be several days old.

In the event of a disaster, the organization can deliver more recent backup data or restore systems through network connections, allowing operations to resume much faster than in a cold site. Warm sites are often chosen by companies that require moderate recovery times and cannot afford to be offline for long but still want to control costs.