Professional Microsoft® SQL Server® 2008 Administration

16.4. Peer-to-Peer Replication

Peer-to-peer is a type of transactional replication. Unlike the traditional replication types, it provides a headless topology, whereby there are multiple publishers and one or more subscribers. In peer-to-peer replication, every participant is both a publisher and a subscriber. It is suitable for cases in which user applications need to read or modify data at any of the databases participating in the setup. It provides an interesting alternative for load-balancing and high-availability scenarios. Note that this feature is available only in the Enterprise Edition of SQL Server 2008. Oracle calls this kind of replication "multimaster," whereas DB2 calls it "update anywhere."

Keep the following in mind when evaluating and setting up peer-to-peer replication:

• It is designed for a small number of participating databases. A good rule-of-thumb number is less than 10. If you use more than that, you could encounter performance issues.

• Unlike merge replication, peer-to-peer replication does not handle conflict resolution.

• Peer-to-peer does not support data filtering. That would defeat its purpose because everybody is an equal partner here for high availability and load balancing.

• Applications can scale out read operations across multiple databases, and databases are always online. Participating nodes can be added or removed for maintenance.

• As mentioned, peer-to-peer replication is available only in Enterprise Edition; however, for your testing purposes, it is ...