In recent discussion I had on this topic, there was a query as below?
“If we are creating vSAN vmkernel port that carries vSAN traffic, in that case why do we need to use vSAN multicast (prior to vSAN 6.6) and Unicast (in vSAN 6.6 and onwards)?”.
In other words, what is really transferred inside multicast or unicast vSAN traffic?
Virtual SAN uses a clustered metadata database and monitoring service (CMMDS) to make metadata available to each host in the cluster. The CMMDS is designed to be a highly available, performant and network efficient service that shares information regarding host, network, disks, objects, components, etc. among all of the hosts within the Virtual SAN cluster. Each host is intended to contain an identical copy of this metadata.
So multicast/unicast is used for metadata operations such as object creation, change in object status after a failure/publication of statistics like significant change of free disk space across all hosts in vSAN cluster.