Disaster Recovery as a Cloud Service

1. Disaster Recovery as a Cloud Service Chao Liu SUNY Buffalo Computer Science

2. How is DR Done Today? A typical DR service works by replicating application state between two data centers; if the primary data center becomes unavailable, then the backup site can take over and will activate a new copy of the application using the most recently replicated data.

3. Disaster Recovery Requirements • Recovery Point Objective • The RPO of a DR system represents the point in time of the most recent backup prior to any failure. • Recovery Time Objective • The RTO is an business decision that specifies a bound on how long it can take for an application to come back online after a failure occurs.

4. Disaster Recovery Requirements Performance Consistency Geographic Separation

5. Disaster Mechanism • State replication can be done at one of these layers: • Within an application • Per disk or within a file system • For the full system context • Replication at the application layer can be the most optimized, only transferring the crucial state of a specific application.

6. Disaster Recovery The level of data protection and speed of recovery depends on the type of backup mechanism used and the nature of resources available at the backup site. 1. Hot Backup Site 2. Warm Backup Site 3. Cold Backup Site

7. Hot Backup Site Provides a set of mirrored stand-by servers These servers are always available to run Provide minimal RTO and RPO Synchronous replication This form of backup is the most expensive Largest impact on normal application performance

8. Warm Backup Site Depend on the necessary RPO Synchronous or asynchronous It may take minutes to bring them online Slows recovery, but also reduces cost

9. Cold Backup Site Data is only replicated on a periodic basis Servers are not readily available A delay of hours or days, resulting in a High RTO

10. Failover and Failback Detect when a disaster has occurred is a challenging problem. Cloud based systems can simplify this problem by monitoring the primary data center from cloud nodes distributed across different geographic regions.

12. DR as a Cloud Service During normal operation, the system stays in Replication Mode. When a disaster occurs, the system enters Failover Mode.

13. Case Study: Multi-tier Web App Cost Breakdown 99% Uptime Cost Cost of Adding DR

16. Case Study: Data Warehouse Cost Breakdown 99% Uptime Cost Periodic Backups

19. Benefits of the Cloud Cloud computing can facilitate disaster recovery by significantly lowering costs The benefits of virtualization, while not necessarily specific to cloud platforms, still provide important features for disaster recovery

20. Challenges for the Cloud Provider Handling Correlated Failures Revenue Maximization

21. Mechanism for Cloud DR Network Reconfiguration Security & Isolation

22. Ongoing Work and Conclusion Cloud computing platforms are an excellent match for providing disaster recovery services due to their pay-as-you-go pricing model and ability to rapidly bring resources online after a disaster. Better understand what features and optimizations must be included within the cloud platform itself, and to explore the tradeoffs between cost, RPO, and RTO in a cloud DR service.

23. Thank You