1 Choosing Disaster Recovery Solution for Database Systems EECS711 : Security Management and Audit Spring 2010 Presenter : Amit Dandekar Instructor : Dr. Hossein Saiedian

2 Contents Database failures types Availability solutions Availability mechanisms Recovery procedures Conclusion

3 Failure types Database failure types – Transient – Crash – Media – Site – Operator – Malicious Least Severe Most Severe

4 Failure types Hardware related Human error Power failure Others Natural disaster DBMS related 30% 25% 20% 16% 6% 3% Source: Forrester Research, Inc.

5 Availability solutions Two categories of availability solutions – Sporadic un-availability of database Mission critical systems Online transaction processing systems – Complete un-availability of database Data warehouse Decision support systems

6 Availability solutions Protect against sporadic unavailability Used to guard against sporadic outages Implementation may be co-located – Geographically distributed to protect against site failure Recovery time is expected to be within minutes or less Recovery point is within minutes or immediate More complicated to deploy and expensive Expensive

7 Availability solutions Protect against complete unavailability Used to guard against disasters Geographically distributed implementation Recovery times within hours or days Recovery point may be within hours or days Relatively less complicated to deploy Less expensive

8 Availability mechanisms Data synchronization – Online synchronization Primary and secondary are always synchronized – Allows immediate primary takeover – Comes with communication and performance overhead Offline synchronization – Offline synchronization Synchronization performed when no active transactions occurring Typically backup site synced periodically – May lose updates in case of disaster

9 Availability mechanisms Data replication – Active replication Data is transferred and processed Can share workload with primary site – Secondary should have enough processing power – Passive replication Data is transferred and stored without processing Typically use Redundant Array of Disks (RAID) – Guards against media failure Remote mirror required to recover from site failure

10 Popular availability solutions 40% 35% 20% 5% Backup tapes Log shipping Mirroring and replication Others Source: Forrester Research, Inc.

11 Disaster recovery procedure Recovery when using active replication or online synchronization – Hot site is made the primary site by system admin Automated fail-over may treat transient failures as disasters – Recovery time can be as short as few minutes

12 Disaster recovery procedure Three common disaster recovery approaches when using off-line or passive mechanisms – Sledgehammer Rebuild entire database from scratch Off-line approach for non-critical, non-volatile data – Behind the back copying Copy and rebuild table spaces and index datasets – Scalpel Performs restoration of data at granular level Restore one table at a time in order of priority

13 Conclusion Evaluate and identify your database availability requirements – Protect against sporadic un-availability – Protect against complete unavailability Choose appropriate availability mechanism as disaster recovery technique – Active replication or online synchronization – Passive replication or offline synchronization

14 References Choy, Manhoi, Hong Va Leong, and Man Hon Wong. "Disaster recovery techniques for database systems." Commun. ACM 43.11es (2000): Yuhanna, Noel. "ForrTel: Making Your Enterprise Database Highly Available." Forrester Research. Forrester Research, Web. 19 Feb