One of the new features in vSAN 6.6 is unicast support. This makes it much easier to deploy VMware’s virtual storage product from a (cloud/multi-site) networking perspective. vSAN has always used multicast for its metadata updates between the hosts in the cluster. With unicast this is done through the vCenter server making it the single source of truth eliminating the need for multicast. But how do we actually enable unicast? This is easier than you might think.
vSAN multicast to unicast
We start of with a vSphere 6.5 GA environment which includes vSAN 6.5. When checking the summary page of the cluster there is no indication of the networking mode used. This is normal because this is not yet displayed in version 6.5 of vSAN as there is only one supported mode.
To use unicast networking in the first place we need version 6.6 of vSAN. The first step is to update vCenter server and the ESXi hosts to at least version 6.5d. We will start with the vCenter update.
As you might know vCenter can be updated directly from the VAMI page.
We will update to the latest version currently available, which is vCenter 6.5e. After this is completed and we check the vSAN cluster summary page again we can now see the networking mode that is used.
The networking mode is still ‘Multicast’ but we have not updated our ESXi hosts yet.
After upgrading the ESXi hosts to the 6.5e release all our components in the cluster are now running version 6.6 of vSAN. When we now check the networking mode in our cluster we should see it running in ‘Unicast’.
Now, how easy was that. We only upgraded our environment and when the last host in our cluster was upgraded the switch to unicast was automagically done.
Please note: When the cluster is running in unicast mode and you add a pre-vSAN 6.6 host, the cluster will switch back to multicast again. This will remain until either the older host is removed or all hosts are of version 6.6.
Removing the need for multicast simplifies the vSAN network design, for local-site, multi-site or cloud environment. It also saves you a conversation with the networking guys. It potentially also saves you time in troubleshooting scenarios. By the way, this is just one of the many new features that are included with vSAN 6.6. For a complete list check the whats new section of the vSAN 6.6 release notes over at VMware.