For all Secondary hosts replicating in synchronous mode, VVR first sends the write to the Primary SRL. VVR then sends the write to the Secondary hosts and waits for a network acknowledgment that the write was received. When all Secondary hosts replicating in synchronous mode have acknowledged the write, VVR notifies the application that the write is complete. The Secondary sends the network acknowledgment as soon as the write is received in the VVR kernel memory on the Secondary. The application does not need to wait for the full disk write, which improves performance. The data is subsequently written to the Secondary data volumes. When the write is completed on the Secondary data volumes, VVR sends a data acknowledgment back to the Primary.

For all Secondary hosts replicating in asynchronous mode, VVR notifies the application that the write is complete after it is written to the Primary SRL. Therefore, the write latency consists of the time to write to the SRL only. VVR then sends the write to the Secondary hosts. The Secondary sends a network acknowledgment to the Primary as soon as the write is received in the VVR kernel memory on the Secondary. When the write is completed on the Secondary data volumes, VVR sends a data acknowledgment back to the Primary.

The application considers the write complete after receiving notification from VVR that the data is written to the Primary SRL, and, for any Secondary hosts replicating in synchronous mode, that the write has been received in the kernel buffer. However, VVR continues to track the write until the data acknowledgment is received from all the Secondary hosts. If the Secondary crashes before writing to the data volumes on the Secondary or if the Primary crashes before it receives the data acknowledgment, the write can be replayed from the SRL.