To ensure redundancy during runtime, the following
components of the Alfresco system must be replicated and/or synchronized
across each cluster:
Level 2 cache
Content store replication
The underlying content binaries are distributed by either sharing a common content store between all machines in a cluster or by replicating content between the clustered machines and a shared store(s). The common store is simpler and more prevalent.
Indexes provide searchable references to all nodes in Alfresco. The index store cannot be shared between servers. To keep the indexes up to date, a timed thread updates each index directly from the database when running in a cluster.
It is possible to have co-located databases which synchronize with each other. To use co-located databases, refer to your database vendor documentation.
Level 2 cache replication
The Level 2 (L2) cache provides out-of-transaction caching of Java objects inside the Alfresco system. Alfresco provides support for EHCache. Using EHCache does not restrict the Alfresco system to any particular application server, so it is completely portable.