One of the most important aspects of disaster recovery is to have a location from which the recovery can take place. This location is known as a backup site. In the event of a disaster, a backup site is where your data center will be recreated, and where you will operate from, for the length of the disaster.
There are three different types of backup sites:
Cold backup sites
Warm backup sites
Hot backup sites
Obviously these terms do not refer to the temperature of the backup site. Instead, they refer to the effort required to begin operations at the backup site in the event of a disaster.
A cold backup site is little more than an appropriately configured space in a building. Everything required to restore service to your users must be procured and delivered to the site before the process of recovery can begin. As you can imagine, the delay going from a cold backup site to full operation can be substantial.
Cold backup sites are the least expensive sites.
A warm backup site is already stocked with hardware representing a reasonable facsimile of that found in your data center. To restore service, the last backups from your off-site storage facility must be delivered, and bare metal restoration completed, before the real work of recovery can begin.
Hot backup sites have a virtual mirror image of your current data center, with all systems configured and waiting only for the last backups of your user data from your off-site storage facility. As you can imagine, a hot backup site can often be brought up to full production in no more than a few hours.
A hot backup site is the most expensive approach to disaster recovery.
Backup sites can come from three different sources:
Companies specializing in providing disaster recovery services
Other locations owned and operated by your organization
A mutual agreement with another organization to share data center facilities in the event of a disaster
Each approach has its good and bad points. For example, contracting with a disaster recovery firm often gives you access to professionals skilled in guiding organizations through the process of creating, testing, and implementing a disaster recovery plan. As you might imagine, these services do not come without cost.
Using space in another facility owned and operated by your organization can be essentially a zero-cost option, but stocking the backup site and maintaining its readiness is still an expensive proposition.
Crafting an agreement to share data centers with another organization can be extremely inexpensive, but long-term operations under such conditions are usually not possible, as the host's data center must still maintain their normal production, making the situation strained at best.
In the end, the selection of a backup site is a compromise between cost and your organization's need for the continuation of production.