VSAN requires a VMkernel interface with the Virtual SAN traffic activated through which the cluster nodes communicate with each other. VSAN traffic comprises of a minimal amount of cluster-related administrative traffic and a large chunk of traffic that is attributed to object-related I/O.
From an IOPS perspective, if a specific block that is read or written to is not available on the local disk group, the I/O will need to traverse the VSAN network to other hosts that hold the referenced block. Furthermore, in the backend, to satisfy the availability requirements, data is being replicated. For instance, if there is a nonrecoverable physical disk failure, the objects residing on the specific disk are likely to have varying tolerance levels. Hence, the components existing on that physical device will be replicated through the VSAN network to make the objects associated with the virtual machine compliant with the policy set.