Enterprise Recovery Time Objectives (RTO) and Recovery Point Objectives (RPO) dictate the depth and extent of disaster recovery planning. The RTO determines how quickly applications need to be made available for business continuity. The RPO establishes the point to which data must be recovered. Tight RTOs and RPOs presuppose the deployment of highly available, sophisticated disaster management programs with essential replication, mirrored, hot, warm or cold sites in place.
Replication sites: Replication sites create replicas of the primary site. This may or may not be real-time or near real-time. The hardware and software of the primary data center is duplicated to improve reliability, fault-tolerance and accessibility. Access to the replicated site is typically uniform with access to a single, non-replicated entity.
Hot Sites: A hot site is a partial or full duplicate of the primary site. The computing infrastructure available at the original site is set up in the hot site. The applications and data in the primary site are backed up near real-time. Mirroring software is used to set up hot sites and synchronize it with the primary site. A hot site is used when an organization cannot tolerate any downtime or has a near-zero RTO and RPO. However, delays may occur as staff work on activating the hot site in the event of a disaster.
Warm site: A warm site is similar to the hot site, but data duplication is not done in real-time. It offers access to space, utilities and equipment. Current backups have to be installed and systems and services will have to be brought online in the event of disaster. Often, warm sites contain only a subset of the computing infrastructure available in the primary site. This is ideal for organizations that have a flexible RTO and RPO.
Cold Site: A cold site is a disaster recovery plan site. It is used to simulate disaster recovery scenarios. The site usually contains sufficient equipment to mount and restore essential IT operations. However, bringing a cold site up can take up to two weeks or longer.
Mobile sites: These are sites that occupy a space between warm and cold sites. The site contains portable structures and the degree of computing equipment deployed determines whether the site is a warm site or a cold site. These sites have limited scope and scale in a disaster recovery scenario. However, these sites make sense for SMBs with less tolerance for delays in resuming IT operations.