adding a node to a 3 node cluster

[SSmalleyIT]

Hi Brains trust...

I have 3 x ESXi nodes and vCenter in an essentials plus bundle and 6 vSAN CPU licenses.

the 3 x nodes have 2 CPU's each, so the vCenter Essentials license and vsan license is at capacity

We have rececently aquired a new Dell R740 vsan ready node (the other servers are dell too).  the old node is an older gen and other 2 nodes in the vSAN are the same Gen and CPU as the new one.  The intention was to replace one of the older nodes with the new one.

However I have discovered that a 3 node cluster does not give full fault protection as per below from https://docs.vmware.com/en/VMware-vSphere/6.7/com.vmware.vsphere.virtualsan.doc/GUID-8491C4B0-6F94-4... 

A minimum of three fault domains are required to support PFTT=1. For best results, configure four or more fault domains in the cluster. A cluster with three fault domains has the same restrictions that a three host cluster has, such as the inability to reprotect data after a failure and the inability to use the Full data migration mode

So i am unable to evacuate the old node then replace with the new.

I have an temp license from vmware giving me 8 x CPU's for the vSAN (which expires in 2 weeks) 

Can I simply apply a trial license for vcenter enterprise to my existing vcenter then reapply the original license once the migration is finished? 

The plan being to bring in the 4th node do a full migration of the old node, put in maintenance mode and remove from the vSAN, then revert all the licenses.

If anyone has any other suggestions it would be greatly appreciated

Thanks

[TheBobkin]

@SSmalleyIT What you advised should work. (Change vC to temporary higher license,  license 8x vSAN CPUs, add node, evacuate node, remove node, switch licenses back to original).

Good luck with it and let us know how it goes.

[SSmalleyIT]

Thanks for the advice.  We plan to proceed with this over the weekend of 15/04-16/04 and will advise on the results

Thanks