Hot Site: A Hot Site can be defined as a backup site, which is up and running continuously. A Hot Site allows a company to continue normal business operations, within a very short period of time after a disaster. Hot Site can be configured in a branch office, data center or even in cloud. Hot Site must be online and must be available immediately.
Hot site must be equipped with all the necessary hardware, software, network, and Internet connectivity. Data is regularly backed up or replicated to the hot site so that it can be made fully operational in a minimal amount of time in the event of a disaster at the original site. Hot Site must be located far away from the original site, in order to prevent the disaster affecting the hot site also.
Warm Site: A Warm Site is another backup site, is not as equipped as a Hot Site. Warm Site is configured with power, phone, network etc. May have servers and other resources. But a Warm Site is not ready for immediate switch over. The time to switch over from the disaster affected site to Warm Site is more than that of a Hot Site. But less cost is the attraction.
Cold Site: Cold Site contain even fewer facilities than a Warm Site. Cold Site will take more time than a Warm Site or Hot Site to switch operation but it is the cheapest option. Cold Site may contain tables, chairs, bathrooms, and basic technical facilities but will require days or even weeks to set up properly and start operation from Cold Site.