I have a few home-labs that I play with on a regular basis. Before vSphere 6.5 went GA, I installed the beta code and created a vSAN stretched cluster using 2 Intel NUCs.
Long story short, hosts were upgraded, new clusters created/migrated to new vCenter, etc. I started running into weird issues, like multicast network partitioning, and not being able to move VMs to the new cluster. I decided to create a new All-Flash cluster and add another node. I was only able to move VMs on that new node.
After digging a little deeper, found out that the 2 pre-existing hosts were not cleaned up properly when I moved things around. They were still showing on stretched cluster mode on.
Cannot complete file creation operation.
Failed to place witnesses. There are currently 0 usable disks and 1 more usable disks are needed in witness node.
Failed to create object.
Turn stretchedClusterMode off by running the following commands on each host.
GET state: vsish -e get /vmkModules/vsanutil/stretchedClusterMode
If 1 then it is enabled. If 0 it is disabled.
If enabled (1), turn off by setting to 0
SET state: vsish -e set /vmkModules/vsanutil/stretchedClusterMode 0