Backup sites are grouped into three main types: cold sites, warm sites, and hot sites. These categories describe how ready the site is and how quickly it can take over operations after a disaster.
Cold site A cold site is the simplest and usually the least expensive form of backup site. It is mainly an empty or lightly equipped facility that has basic infrastructure such as space, power supply, network cabling, air conditioning, and sometimes raised floors for server rooms. However, it normally does not include active computer systems, installed applications, or up‑to‑date copies of data. When a disaster happens, the organization must move in equipment, install systems, and restore data backups before work can resume. This means that recovery at a cold site can be slow, often taking days or even weeks, depending on the complexity of the systems and the availability of hardware. Because the ongoing costs are low, cold sites are often used by smaller organizations or those that can tolerate longer downtime.
Warm site 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, more recent backup data is delivered or restored over the network, so the organization can start operations faster than at a cold site. Recovery time at a warm site is often measured in hours or a day, which can be acceptable for many businesses or services that do not require instant
failover. Costs are higher than a cold site because some systems are maintained in advance, but they are lower than a hot site.
Hot site A hot site is the most advanced and expensive type of backup site. It is a near duplicate of the original site of the organization, including full computer systems as well as complete backups of user data. Real-time synchronization between the two sites may be used to completely mirror the data environment of the original site using wide-area network links and specialized software. Following a disruption to the original site, the hot site exists so that the organization can relocate, with minimal losses to normal operations in the shortest recovery time. Ideally, a hot site will be up and running within a matter of hours. Personnel may need to be moved to the hot site, but it is possible that the hot site may be operational from a data-processing perspective before staff has relocated. The capacity of the hot site may or may not match the capacity of the original site depending on the organization's requirements. This type of backup site is the most expensive to operate. Hot sites are popular with organizations that operate real-time processes such as financial institutions, government agencies, and eCommerce providers. The most important feature offered from a hot site is that the production environment(s) is running concurrently with the main datacenter. This synchronizing allows for minimal impact and downtime to business operations. In the event of a significant outage, the hot site can take the place of the affected site immediately. However, this level of redundancy comes with a high cost, and businesses will need to weigh the cost-benefit-analysis (CBA) of hot site utilization. Maintaining duplicate hardware, software, and continuous synchronization requires investment and ongoing maintenance. These days, if the backup site is down and misses the "proactive" approach, it may not be considered a hot site depending on the level of maturity of the organization regarding the
ISO 22301 approach (international standard for Business Continuity Management). As a result, hot sites are typically reserved for critical systems where downtime cannot be tolerated. == Alternate sites ==