Understanding Bunker replication

Volume Replicator supports different modes of replication; synchronous and asynchronous. You can use these modes of replication to obtain a complete Disaster Recovery (DR) solution by maintaining additional synchronous Secondaries at a location closer to the Primary.

The synchronous mode of replication enables you to replicate data to an additional Secondary DR site that is located closer to the Primary. That is, in the case of a disaster at the Primary site, it should be possible to start business from the Secondary site without any loss of data, using the synchronous additional Secondary. However, if the additional Secondary is at least 300 miles away from the Primary site, there may be some network write latency, which degrades the input or output performance of the application. In this case the Recovery Time Objective (RTO) depends on the amount of time you need to recover. For example, if the data needs 2 hours to recover, the RTO is 2 hours. In addition, you also have the overhead of maintaining an additional Secondary site. The asynchronous mode of replication does not incur network write latency. During normal operations, the data on the additional Secondary site may not be up-to-date. If a disaster occurs, it is possible that some of the data may not be available at the disaster recovery site and thus zero RPO is not achieved. Besides, maintaining an additional Secondary can result in additional cost overheads.