RPO = Recovery Point Objective
RTO = Recovery Time Objective
WRT = Work Recovery Time
MTD = Maximum Tolerable Downtime
Stage 1 : Business as Usual
At this stage all systems are running production and working correctly.
Stage 2: Disaster Occurs
On a given point in time, disaster occurs and systems needs to be recovered. At this point theRecovery Point Objective (RPO) determines the maximum acceptable amount of data loss measured in time. For example, the maximum tolerable data loss is 15 minutes.
At this stage the system are recovered and back online but not ready for production yet. The Recovery Time Objective (RTO) determines the maximum tolerable amount of time needed to bring all critical systems back online. This covers, for example, restore data from back-up or fix of a failure. In most cases this part is carried out by system administrator, network administrator, storage administrator etc.
Stage 4: Resume Protection
At this stage all systems are recovered, integrity of the system or data is verified and all critical systems can resume normal operations. The Work Recovery Time (WRT) determines the maximum tolerable amount of time that is needed to verify the system and/or data integrity. This could be, for example, checking the databases and logs, making sure the applications or services are running and are available. In most cases those tasks are performed by application administrator, database administrator etc. When all systems affected by the disaster are verified and/or recovered, the environment is ready to resume the production again.
This is of course a simple example of a Business Continuity/Disaster Recovery plan and should be included in your Business Impact Analysis (BIA).