Local Continuous Replication (LCR) with Exchange 2007

Local Continuous Replication is a method to provide a highly available solution for the Databases with a single server solution without the need to perform clustering. Its primary benefit is seen as providing for redundant copies of the database. In the event one copy of the database is corrupted and alternate copy can be manually failed to by the Exchange administrator resulting in minimal down time possible consisting of only a few minutes. This solution is seen with the following primary caharterisics.

• One machine
• Manual activation
• Two copies of the database
• Data validation of the transaction logs
• High Availability
• Requires One datacenter
• Easy configurable
• Minimum Resource requirements

Local continuous replication (LCR) is a single-server solution that uses asynchronous log shipping technology to create and maintain a copy of a storage group on a second set of disks that are connected to the same server as the production storage group.

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LCR provided for transaction log shipping, transaction log replay, and a method to manually switch to a second copy of the Exchange databases in the event of corruption of the first copy.

LCR has the following benefits

1. Reduces the number of backups that are needed
2. Reduces the need for daily full backups
3. Reduces the need to complete backups against the production database by allowing backups on the copy
4. Increases performance of the non-production database by allowing backups of the copy, which can significantly reduce IO
5. All four backup types are supported to include
   1. Full
   2. Copy
   3. Incremental
   4. Differential
6. The LCR copy of the databases becomes the initial defense against a production database failure. In such a circumstance it would take a failure of both the production storage group and the storage group copy before a restoration of tape would be required.
7. Fast recovery from disasters (typically less than ten minutes). Typically, the recovery occurs with little or no data loss
8. Support for larger mailbox quotas, which is achieved as a result of fast recovery that is independent of database size.

Exchange Backups and LCR

Exchange-aware backups are supported for active storage groups and databases and passive database copies. A common task during Exchange-aware backups is the truncation of transaction log files after the backup has completed successfully. The replication feature in LCR guarantees that logs that have not been replicated are deleted. The implication of this behavior is that running backups in a mode that deletes logs may not actually free space if replication is sufficiently far behind in its log copying. Exchange-aware backups in this configuration can either be performed using streaming or VSS backup solutions.

Exchange Restores and LCR

Exchange-aware restores are supported for active and passive databases in an LCR configuration. Exchange-aware restores can either be performed using streaming or VSS backup solutions.

Databases Restore

Before restoring a database from a storage group that was configured for LCR, disabling LCR for the storage group is required. After the restore has completed, the storage group can be reconfigured to use LCR. LCR should be disabled automatically for databases that are being restored.