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Azure SQL Database Business Continuity

Updated: November 6, 2014

Business continuity is the ability to continue business operations when a crisis or disaster occurs. Business continuity planning requires processes, procedures, and measures to ensure that business operations can continue without interruption. This topic focuses on the Azure SQL Database features that enable business continuity and disaster recovery.

By storing your data in Azure SQL Database, you take advantage of many fault tolerance and secure infrastructure capabilities that you would otherwise have to design, acquire, implement, and manage. Azure SQL Database has a built-in high availability subsystem that protects your database from failures of individual servers and devices in a datacenter. Azure SQL Database maintains multiple copies of all data in different physical nodes located across fully independent physical sub-systems to mitigate outages due to failures of individual server components, such as hard drives, network interface adapters, or even entire servers. At any one time, three database replicas are running—one primary replica and two or more secondary replicas. Data is written to the primary and one secondary replica using a quorum based commit scheme before the transaction is considered committed. If the hardware fails on the primary replica, Azure SQL Database detects the failure and fails over to the secondary replica. In case of a physical loss of a replica, a new replica is automatically created. So there are always at minimum two physical, transactionally consistent copies of your data in the datacenter.

On top of the built-in systems that enable high availability of your database, Azure SQL Database offers additional business continuity features.

 

  Basic Standard Premium

Point-in-time restore

Any restore point within the past 7 days

Any restore point within the past 14 days

Any restore point within the past 35 days

Geo-restore

RTO* < 24 hours

RPO† < 24 hours

RTO* < 24 hours

RPO†< 24 hours

RTO* < 24 hours

RPO† < 24 hours

Standard geo-replication

Not included

RTO* < 2 hours

RPO† < 30 minutes

RTO* < 2 hours

RPO† < 30 minutes

Active geo-replication

Not included

Not included

RTO* < 1 hour

RPO† < 5 minutes

* Recovery Time Objective (RTO) - Maximum downtime before the application is fully functional after a failure.

† Recovery Point Objective (RPO) - Maximum amount of most recent data changes (time interval) the application could lose before it is fully functional after a failure.

Point-in-time restore

Point-in-time restore is the most basic restore option, which you get automatically with basic, standard, and premium databases. You can use point-in-time restore to return your database to an earlier point in time. Go back 7 days with basic, 14 days with standard, and 35 days with premium. See Azure SQL Database Backup and Restore and Azure SQL Database Point in Time Restore (blog) for more information. Watch the video Restore a SQL Database Using Point in Time Restore to see how easy it is to use point-in-time restore.

Geo-restore

Geo-restore is similar to point-in-time restore. You also get it automatically with basic, standard, and premium databases. Geo-restore, however, is designed to be a basic recovery option when a database is unavailable because of a large scale incident or outage in the region where your database is hosted. The feature uses Azure read-access geo-redundant storage to store the most recent daily backup of your databases in a different geographical location. Consider geo-restore as a basic disaster recovery solution if your application can tolerate up to 24 hours downtime and data loss. For more information, read Azure SQL Database Geo-Restore (blog), and watch the video Restore a SQL Database Using Geo-Restore to see how to recover a database using geo-restore.

Standard geo-replication

Standard geo-replication is available for standard and premium databases. It’s designed for less write-intensive applications that nevertheless process high volumes of data and have more aggressive recovery requirements than geo-restore can offer. When the primary database fails, it shows as degraded, and you can initiate failover to a non-readable secondary database stored in a different region. For more information, see Standard Geo-Replication for Azure SQL Database and Azure SQL Database Standard Geo-Replication (blog), which has a thorough comparison of active geo-replication and standard geo-replication.

Active geo-replication

Active Geo-Replication is available for premium databases. It’s designed for write-intensive applications with the most aggressive recovery requirements. Using active geo-replication, you can create up to four readable secondaries on servers in different regions. These secondaries are maintained as continuous copies of the primary, and you can initiate failover to a secondary in the same way as standard geo-replication. Active geo-replication provides the highest degree of resiliency to temporary connection problems and high latency, so can support online application upgrade or relocation scenarios, as well as load balancing for read-only workloads. For more information, see Active Geo-Replication for Azure SQL Database and Spotlight on SQL Database Active Geo-Replication (blog).

Additional business continuity features

  • Database copy allows you to create a copy of a database either on the same or different servers in the same or different regions. The copy is transactionally consistent with the source when the database copy operation is complete. It is however a one-time copy, and not continuously replicated from the source. The feature can be used for data migration or ad hoc copy needs. For more information, see Copying Databases in Azure SQL Database.

  • The import and export service lets you manually or automatically export a BACPAC file, which contains a logical copy of data and schema of a database, and then import the file to restore the database. Use import and export for Web and Business databases, which do not support other business continuity features. Or use it in addition to other business continuity features for long-term storage of daily backups or to retain backups beyond the retention period for point-in-time restore. For more information, see How to: Use the Import and Export Service in Azure SQL Database

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