Performance of a cluster depends on the latency and bandwidth of the interconnect. At least dual 1Gbit ethernet is recommended for each node. Thus a cluster should be on a single local or system area network.

If regional copies are needed, we would replicate between clusters by asynchronous log shipping. This requires some custom engineering.

When a transaction is committed at one site, it is logged and sent to the subscribing sites if they are online. If there is no connection, the subscribing sites will get the data from the log. This scheme now works between single Virtuoso servers, and needs some custom development to be adapted to clusters.

If replicating all the data of one site to another site is not possible, then application logic should be involved. Also, if consolidated queries should be made against large, geographically-separated clusters, then it is best to query them separately and merge the results in the application. All depends on the application level rules on where data resides.