Under normal operating conditions, application writes are logged to the Primary SRL and synchronously replicated to the bunker and any other synchronous Secondaries. Thus, the bunker is in the role of a Secondary. A write is completed to the application as soon as it is logged to the Primary SRL, other synchronous Secondary sites, and the bunker SRL. VVR asynchronously writes the data to the Primary data volume and sends it to the asynchronous Secondary. When the Secondary acknowledges the writes, the SRL header is updated to indicate the status of the Secondary.
In a typical asynchronous replication setup, the network bandwidth is provisioned for the average application write rate. Therefore, the bunker SRL may contain some writes that the application considers complete, but that have not been applied to the Secondary.
For synchronous replication, the network bandwidth must be provisioned for peak application write rate.
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