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Disaster Recovery in SQL Server

Disaster Recovery in SQL Server. Rajib Kundu http://www.Citagus.com. Agenda. Definitions Failover Cluster Database Snapshots Log shipping Database Mirroring. Definitions.

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Disaster Recovery in SQL Server

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  1. Disaster Recovery in SQL Server Rajib Kundu http://www.Citagus.com

  2. Agenda • Definitions • Failover Cluster • Database Snapshots • Log shipping • Database Mirroring

  3. Definitions “Disaster recovery planning is the work that is devoted to preparing all the actions that must occur in response to a disaster. The planning includes the selection of a strategy to help recover valuable data. The selection of the appropriate disaster recovery strategy depends on your business requirements.”

  4. Disaster Recovery Comparisons

  5. Prepare a DRP document • Include every possible information: • System architecture (How the system/application works) • How many systems are involved and what their names are. • Their IP Addresses, drive information, file locations • Software installed, Contact information of DBA’s, or other key people. • Know your SLAs and choose appropriate technology.

  6. Prepare a DRP document(cont.) • Include every possible information… • Step by step guide on how to recover each of your system based on different disaster scenarios (Including timelines for recovery) • Security information, jobs/schedule information, etc. • Make it a reminder for self that any system changes should be updated in this guide. • Test, test and test!!!

  7. Failover Clustering

  8. Log Shipping • An automated method of maintaining a warm standby server • Based on SQL Server's backup and restore architecture. Uses the transaction log to track changes • Relatively low-tech and inexpensive • ‘Ships' (copies and restores) a production server's transaction logs to a standby server

  9. Log Shipping (Key terms) • Primary Server: • Contains your primary database. • SQL Server Agent makes periodic transaction log backups to capture changes. • Secondary Server • Contain an unrecovered copy of the production database. • One standby server can contain standby databases from multiple primary servers.

  10. Log Shipping (Key terms) cont… • Monitor Server (Optional) • Monitors the status of the log-shipping jobs on the primary and each standby server. • One monitoring server can monitor multiple primary-standby server pairs. • Should use a server other than the primary or the standby to detect problems on either server.

  11. Log Shipping

  12. Database Mirroring • Newly introduced with SQL Server 2005. • Maintains a copy of the principal database as a mirror. • Transfers log records from principal to mirror server instance. • Works with all hardware that supports SQL Server 2005. • Automatic client redirection (using .NET 2.0) • Can have a third optional server called Witness server for Auto Failover.

  13. Database Mirroring -Synchronous 1 Acknowledge Commit 7 Acknowledge 6 Constantly redoing on mirror 2 Transmit to mirror 2 4 Write to local log Committed in log Write to remote log 3 5 DB Log Log DB

  14. Database Mirroring Enhancements • Enhancements in SQL 2008 • Compression of stream data for which at least a 12.5 percent compression ratio can be achieved. • Automatic Recovery from Corrupted Pages. • Page read-ahead during the undo phase. • Improved use of log send buffers.

  15. General Recommendations • Backup your system databases after modifications. • Test if backups are restorable. • Practice / Test your disaster recovery plans. • Documentation is not only for you. • Keep dedicated DR Server ready. • Use BACKUP CHECKSUM features. • Run DBCC CHECKDB regularly. • Don’t ignore any runtime errors.

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