22.2. Defining the Type of Rollover

Disaster recovery, as the introduction says, is the process for transitioning from one system to another system with as little interruption of service as possible. That's called a rollover, and there are three different ways of doing a rollover:

The obvious difference in the types of rollover is the time and expense necessary to set up the backup site. Hot and warm sites have higher initial expenditures to set up and run.

A mix of rollover types can be used, depending on the specific disaster scenario being planned. For example, a rollover plan for the loss of a single server could use a hot rollover easily and relatively cheaply by creating and keeping a virtual machine copy of the Directory Server instance which can be brought online within minutes. It would not even require keeping the virtual machine in a separate facility or network. On the other hand, a cold rollover could be planned for the loss of an entire data center or office.

Match the rollover process to the severity of the disaster scenario, your budget and available resources, and the likelihood of encountering problems.