6.8.6 Memory-to-memory replication configuration
Memory-to-memory replication enables the sharing of sessions between appservers without using a database. Memory-to-memory replication is based on the Data Replication Services (DRS) of WAS V6 which allows the definition of replication domains whose members can have their HTTP sessions replicated among themselves.
The benefits of using memory-to-memory replication rather than a database for session persistence...
- The overhead and cost of setting up and maintaining a real-time, production database, such as preparing a machine, installing and configuring a database, starting and so on, is not needed.
- The database becomes a SPOF (Single Point Of Failure) for session persistence and certain cost and effort is required to solve this issue at the database level. However, it was found that database persistence might perform better than a badly configured memory-to-memory replication. (Session state)
All features available in database persistence are available in memory-to-memory replication as well, except for DB2 variable row size and multi-row features, which are features specific to a database.
To effectively deploy memory-to-memory replication in clustered environments, especially large ones, implementers must think carefully about how to exactly configure the replicator topology and settings. If care is not taken then the amount of memory and resource usage taken by session replication can increase significantly.
See Understanding DRS (Data Replication Services)