Cloud Application Architectures

Disaster Recovery

Disaster recovery is the art of being able to resume normal systems operations when faced with a disaster scenario. What constitutes a disaster depends on your context. In general, I consider a disaster to be an anomalous event that causes the interruption of normal operations. In a traditional data center, for example, the loss of a hard drive is not a disaster scenario, because it is more or less an expected event. A fire in the data center, on the other hand, is an abnormal event likely to cause an interruption of normal operations.

The total and sudden loss of a complete server, which you might consider a disaster in a physical data center, happens—relatively speaking—all of the time in the cloud. Although such a frequency demotes such events from the realm of disaster recovery, you still need solid disaster recovery processes to deal with them. As a result, disaster recovery is not simply a good idea that you can keep putting off in favor of other priorities—it is a requirement.

What makes disaster recovery so problematic in a physical environment is the amount of manual labor required to prepare for and execute a disaster recovery plan. Furthermore, fully testing your processes and procedures is often very difficult. Too many organizations have a disaster recovery plan that has never actually been tested in an environment that sufficiently replicates real-world conditions to give them the confidence that the plan will work.

Disaster recovery in the cloud can ...