Couchbase Server 2.0 supports cross datacenter replication (XDCR), providing an easy way to replicate data from one cluster to another for disaster recovery as well as better data locality (getting data closer to its users).

Couchbase Server provides support for both intra-cluster replication and cross datacenter replication (XDCR). Intra-cluster replication is the process of replicating data on multiple servers within a cluster in order to provide data redundancy should one or more servers crash. Data in Couchbase Server is distributed uniformly across all the servers in a cluster, with each server holding active and replica documents. When a new document is added to Couchbase Server, in addition to being persisted, it is also replicated to other servers within the cluster (this is configurable up to three replicas). If a server goes down, failover promotes replica data to active:

Figure 5.9. Replication within a Cluster

Cross datacenter replication in Couchbase Server involves replicating active data to multiple, geographically diverse datacenters either for disaster recovery or to bring data closer to its users for faster data access, as shown in below:

Figure 5.10. Cross Data Center Replication

You can also see that XDCR and intra-cluster replication occurs simultaneously. Intra-cluster replication is taking place within the clusters at both Datacenter 1 and Datacenter 2, while at the same time XDCR is replicating documents across datacenters. Both datacenters are serving read and write requests from the application.