Multi-site Deployment

Both embedded peer-to-peer clusters and SQLFire server clusters are tightly-coupled by design. When members of a SQLFire cluster must share data with each other, scalability problems are magnified if the members span multiple networks that are spread out geographically across a WAN. To address this issue, SQLFire extends the client-server deployment model by providing highly-available gateways that replicate data to remote clusters in a hub-spoke model.

Understanding Multi-site Deployment

The vFabric SQLFire multi-site implementation loosely couples individual SQLFire distributed systems by using gateways. A gateway is a logical connection between systems that replicates DML operations for configured tables. The gateway between systems is tolerant of weak or slow physical connections between distributed system sites. All data exchange occurs asynchronously without any loss of data or loss of event ordering.

Although the figure above shows only two SQLFire clusters joined by a gateway, you can daisy-chain multiple distributed systems simply by adding more gateways to your deployment.

Deciding When to Use Multi-site Deployment

A wide-area network (WAN) is the main use case for the multi-site topology. The multi-site topology enables systems at disparate geographical locations to replicate DML operations for configured tables and provide a coherent view of the tables' data. It also ensures independence of the systems, so if any are lost from view, the remaining systems continue to operate.

The WAN model is generally deployed either for data visibility across multiple data centers, or as a mechanism for disaster recovery. Client applications can connect to the SQLFire cluster in the local data center, but if visibility to the cluster is lost, then those clients can fail over to any other cluster that replicates data using a gateway. A multi-site deployment requires a vFabric SQLFire Enterprise license for each data host in each site.