Guide to Disaster Recovery Terms
There are many interpretations to these terms; we’ve gone ahead and tried to make them as succinct as possible.
Recovery Time Objective: (RTO) the maximum period of time an affected user can function without having access to the business function or application. This means taking into account factors like network access and security parameters before declaring an application recovered.
Recovery Point Objective: (RPO) the maximum amount of data an application "owner" is prepared to lose. This is typically measured in hours; however, if the application in question’s workload varies throughout a 24-hour period it may be possible that an RPO target varies as well.
In addition to RTO and RPO, there are two other key terms often misunderstood and often incorrectly used.
Restorable: applications that can only be re-built to the last available backup’s completion.
Recoverable: applications that can be re-built to the point where the original disaster occurred. A recoverable environment is much more advantageous to an organization than a restorable solution; yet today, most organizations are still using restore-centric services.
Always On Architecture: an application and its supporting infrastructure designed to tolerate failure with minimal disruption to its users.
Transactional Data Integrity: The ability for an application to duplicate transaction data to a second/remote site without the use of Third Party tools or costly professional services is a key item to consider when architecting a bet-the-business application. A rule of thumb is always replicating data as close to the native transaction as possible.
Reference Data Integrity: All non-transactional data and information that is part of an application's data set.
System State: The metadata associated with how an application and its supporting operating systems are configured. System state is required to reconstitute a functioning environment.
Accessibility: In its most basic form, an application's intended user can reach the application without interruption exceeding the particular application's RTO.