There seems to be a bit of confusion on how the upgrade from an existing vCenter Server Appliance (VCSA) 5.5/6.0 to the upcoming VCSA 6.5 release will work. I suspect part of the confusion is also due to the fact that the underlying OS in the VCSA in vSphere 6.5 is changing from SLES to VMware's very own Photon OS. Before going into the upgrade details, I do want to mention that with this change, VMware will now own the entire software stack within the VCSA (OS + Application). This will allow VMware to quickly respond and deliver OS and security updates to customers at a much quicker rate than it was possible before. In addition, Photon OS is also a very optimized Linux distribution which has allowed VMware to significantly improve the reboot and startup time of the vCenter Server application. To be clear, the vCenter Server application itself is NOT running as a Docker Container nor are there any other application or services within the VCSA that is running a Docker Container, I know this was something folks were also assuming because the OS changed to Photon OS.
Now going back to the upgrade question, how would an upgrade work if the underlying OS is changing? The answer is actually quite simple. VCSA upgrades are "Migration" based upgrades and has been since the very first release of the VCSA in vSphere 5.0.
So how does it work? Here is the high level workflow:
- The new VCSA 6.5 is deployed using the standard VCSA UI or CLI installer using the "Upgrade" option. It does require a temporarily IP Address (DHCP or Static)
- The VCSA 6.5 then connects to the existing VCSA 5.5/6.0 and starts copying (migrate) the data from the old VCS to the new VCSA
- The existing VCSA 5.5/6.0 is then shutdown, the new VCSA 6.5 now takes over the personality of the original VCSA and you have now successfully upgraded
As you can see from this workflow, your existing VCSA is not actually being upgraded but rather its data is migrated over to the new VCSA. Once the upgrade has completed, you will now be on the new Photon OS based VCSA. Hopefully this clears up any confusion 🙂
Lastly, I should also mention that in vSphere 6.5, we have an updated version of the VCSA Migration Tool simliar to the one release with vSphere 6.0 Update 2m. It will now support migrating from a Windows-based vCenter Server running either vSphere 5.5 or vSphere 6.0 to VCSA 6.5.