VSAN and vSphere 6.5…
There is a not so nice feature in vSphere 6.5 which makes VSAN explicitly dependent on vCenter. It is detailed in the release notes but easily overlooked… http://pubs.vmware.com/Release_Notes/en/vsan/66/vmware-virtual-san-66-release-notes.html
Fixed in the latest update of vSphere/vCenter, but just be aware of the following steps before bouncing vCenter for maintenance or upgrade…