In a stretched cluster, the primary node is located at the preferred site.

In a fault domain, CMMDS data must be communicated from the secondary site to the preferred site. To calculate the traffic in a stretched cluster, you must multiply the number of nodes in a secondary site with the CMMDS node size (in MB) to the number of nodes in the secondary site.

Traffic in a stretched cluster = number of nodes in the secondary site * CMMDS node size (in MB) * number of nodes in the secondary site.

With the unicast traffic, there is no change in the witness site traffic requirements.