This section explains how VVR processes an incoming write when replicating in asynchronous mode with secondary logging.
Figure: Example - how data flows in the asynchronous mode of replication with secondary logging shows how data flows in the asynchronous mode of replication.
In the asynchronous mode of replication with secondary logging, VVR processes an incoming write by performing the following steps in the order listed below:
VVR receives a write on the Primary.
Writes it to the Primary SRL.
On the Primary, acknowledges to the application that the write is complete.
Sends the writes to the asynchronous Secondary hosts, in the order in which they were received on the Primary, and at the same time, writes to the Primary data volumes.
When the Primary receives the network acknowledgment, it knows that the write has been received in the Secondary VVR memory buffer.
VVR sends the write to the Secondary SRL and then sends a data acknowledgment to the Primary.
In parallel, the Secondary issues the write to the data volumes on the Secondary data volume. This write is queued and started in parallel with other queued writes to the data volume.
When the Primary receives the data acknowledgment, VVR marks the write as complete in the SRL.