Adding an esxi 7.0u3 to an existing 6.7u3 cluster.

[Knothead00]

Can I add a esxi 7.0u3 to an existing vSAN clustering using (7) ESXi 6.7 P02 (build 16075168)  servers.?

Roger.  Thanks.

[Knothead00]

The vCenter is at 7.0.3 build 20150588

disk management version of the vSAN is 10.

[TheBobkin]

@Knothead00 You can but is it not advisable - what is your reason for doing this?

If you are going to do this then it must have zero disks with vSAN partitions on them when it is joined to the cluster and you should set Virsto legacy disk format to v10 on that node https://kb.vmware.com/s/article/2146221 (and later you can revert this to default after the other nodes are updated to 7.0 U3, assuming that is the plan).

If you don't do that then it could result in CMMDS version getting bumped to v15 which will mean it will get isolated from the cluster and can never rejoin the other nodes in the cluster (until they were also on 7.0 U3) https://kb.vmware.com/s/article/76841

Also, Roger, thanks for posting questions with specific details (like build numbers not just 'ESXi 6.7 :D)  that can be relevant, this saves time and increases odds of better answers.

[Knothead00]

I was hoping to add (6) 7.0 esxi servers to the cluster then remove the (6) 6.7 servers from the cluster. I was do not what to tear down the cluster and rebuilt due to the VMs running on it.

From what you are saying is it is best to upgrade the current (6) 6.7 servers to 7.0u3 then add the newer servers .

[TheBobkin · Accepted solution]

@Knothead00 Yes, upgrading the nodes to be decommissioned before adding the new ones would be the best option - this may avoid other complications such as EVC mode migrations etc. .

That being said, I have worked with customers doing exactly what you proposed and if going with that option then applying the points I mentioned above should work (as it did for them).

[Tibmeister]

That major of a bump, I would recommend creating a new cluster for the 7.x and once configured, migrate the VMs to the new cluster.  It's really the safest option as long as you ensure the EVC mode of the old cluster and new cluster match.  Then, once done you can tear down the old cluster and rename the new cluster.

There's not a ton that is so engrained in the cluster that, in my mind, warrants the risk and headache of putting new hosts in the existing cluster when there's that much difference in version. vDS is a Datacenter construct and can be shared across multiple clusters, so really the only thing would be storage and with vSAN, probably best to keep them completely isolated to avoid any weird compatibility issues or accidents.