With a firm understanding of RPO (how much data I can afford to lose) and RTO (how long I can afford to be down) from the last DR session, our next task in a disaster recovery strategy is to assign RPO/RTO values to each application in the environment. Before we do that, however, it would be best if we grouped applications together and applied RPO/RTO policy to the groupings. We call these groups of applications “tiers”, and there are many models for this. For now we’ll use the three-tier model, with Tier 1 being the most critical and Tier 3 being the least. As explained in the video, the RPO/RTO values typically range from 15 minutes for Tier 1 workloads to upwards of 72 hours for Tier 3 workloads. However, these times should be customized for your organization’s needs.
Finally, we want to assign technologies to each individual tier. For Tier 3, we’ll usually rely on nightly backups to get us back up and running in the event of a disaster. For Tier 2, SAN-based replication is best, but more frequently-taken backups will also suffice. Tier 1 is sometimes handled by rapid backups, but the best solution is deploy DR software such as Zerto or VMware SRM. By leveraging the appropriate technology with each tier, we can optimize budget spending and deliver the class of service required for each application in the data center.