I was just reading this blog.
It is coincidental, because I will be starting to upgrade to v6.5 U3 this week. Our vCenters are currently in ELM with 4 PSCs. We are mixed at v6.5 U1 and v6.5U2.
So it seems reading this I have to upgrade the v6.5 U1 to U2 first, and then apply the last U2 patch. And then upgrade to U3? And the v6.5U2 I need to patch the last U2 patch and then apply U3?
I could have sworn I have not done this before and jumped around in earlier releases. Thank you.
It's not supported to run these mixed versions in ELM for long periods of time–any longer than it takes to get them all upgraded. So your first order of business should be, I think, to get them all to U2 (both PSCs [first] and vCenters). From there, begin the update to U3 but ensure you do it in an even capacity so they all eventually get to the same patch. Doing otherwise may have unintended consequences.