27.2. Cross-Datacenter Replication Operations

Red Hat JBoss Data Grid's Cross-Datacenter Replication operation is explained through the use of an example, as follows:

Three sites are configured in this example: LON, NYC and SFO. Each site hosts a running JBoss Data Grid cluster made up of three to four physical nodes.

The Users cache is active in all three sites. Changes to the Users cache at the LON site is replicated at the other two sites. The Orders cache, however, is only available locally at the LON site because it is not replicated to the other sites.

The Users cache can use different replication mechanisms each site. For example, it can back up data synchronously to SFO and asynchronously to NYC and LON.

The Users cache can also have a different configuration from one site to another. For example, it can be configured as a distributed cache with numOwners set to 2 in the LON site, as a replicated cache in the NYC site and as a distributed cache with numOwners set to 1 in the SFO site.

JGroups is used for communication within each site as well as inter-site communication. Specifically, a JGroups protocol called RELAY2 facilitates communication between sites. For more information, see Section B.4, “About RELAY2”