The following use cases demonstrate the strategy of replicating both system and user databases:
PowerFlex replication disaster restart solution
PowerFlex provides native asynchronous consistent replication for disaster restart solution. Ensure that the following prerequisites are met for the disaster restart solution:
- All the database datafile and transaction log storage volumes must be in a single RCG. It is possible to include more than a single database in an RCG.
- The replication is in a consistent state.
The following are additional considerations and recommended best practices:
- For restart solution alone, It is not required to separate the datafiles from transaction logs of each database. They need to be replicated in a single RCG. However, it is still recommended to separate data and transaction logs to their own volumes for ease of performance monitoring and controls.
- During active replication, the remote volumes are not accessible to the remote servers. To ensure that the remote servers are aware of them, or even more importantly, to test the disaster restart strategy, it is recommended to use the PowerFlex Test Failover feature. This feature does not stop the replication, Instead, it automatically creates a remote snapshot and maps it to the same target volumes of the replication, making them read-writable. Therefore, one or more remote servers can discover the remote volume and disaster restart testing can be performed. When the Test Failover is finished, the snapshot is discarded.
By following these requirements and best practices, PowerFlex replication offers an easy to use, comprehensive restart solution including a stand-alone SQL Server instance, or a SQL Server instance that is part of WSFC and FCI.
Note: PowerFlex replication can include additional databases, message queues, and external data in the RCG containing the SQL Server databases, keeping all of them consistent.
PowerFlex replication can be extended to create remote database copies for purposes such as to run database reports, create test and development environments, performance testing, and so on. This is done without disturbing the PowerFlex replication by using remote PowerFlex snapshots. PowerFlex snapshots are coordinated with PowerFlex asynchronous replication to ensure that the remote snapshot data is consistent. Ensure that the following prerequisites are met for the remote instance creation solution:
- Remote PowerFlex snapshots must be taken at an RCG granularity.
- Since all the transaction log and datafiles of one or more databases are fully contained within the RCG, and since PowerFlex snapshots are consistent across their volumes, the remote snapshots satisfy the requirements for a restart solution.