Using Join Sites for migrating servers - why do servers need to be same operating system? I'm migrating to upgrade the operating systems

[AmyBrassieur]

Well, I'm back.

I'm hoping to use the Join Sites strategy to migrate my portal and servers. Then I came across the following which says the join sites server has to have same operating system and hardware specs as the existing servers in the site. 

The reason I'm migrating is to get a more updated operating system that is supported with the later versions of portal and server. I want to go from Windows 2008 R2 on the Portal server and Windows 2012 on the Server to Windows 2019. 

I was thinking of installing both Portal and Server on a new single larger VM, joining each to my existing Portal and Server sites. But the new VM won't have the same operating systems or hardware specs. 

Do I have to give up my Join Site strategy because of this?

Just found this page: https://enterprise.arcgis.com/en/server/10.9.1/deploy/windows/join-a-machine-to-a-site.htm

Where it has this paragraph: 

Considerations before joining a site

The Join Site operation adds a new machine to an existing ArcGIS Server site. This can be done temporarily to migrate to new machines, or more permanently to increase the resources and processing power of your server site. If you are using Join Site to migrate, the new and existing machines do not need to match, but if you intend to keep all machines in the site, it is recommended that you ensure they meet the following criteria:

• The new machine must be running on the same operating system platform as the other ArcGIS Server machines in the site. It is recommended that you use the same operating system version and hardware resources for all machines in your site. For example, if you have a site comprised of ArcGIS Server machines, each running on Windows Server 2008 R2 with a 3 GHz processor and 8 GB of RAM, the machine you add to the site should also have the same operating system and hardware specifications.

[Brian_Wilson · Accepted solution]

I think you missed this line

"If you are using Join Site to migrate, the new and existing machines do not need to match"

They have to match only if you will be using multiple machines, because it makes load balancing easier.

Personally I think having Portal and Server on separate machines is better but that's your call. When I open a ticket with support they inevitably want me to be able to roll back to a snapshot and if I do that it affects everything on that VM. So, I prefer to keep things separated out.

[AmyBrassieur]

Oh, thanks, I was reading too fast.  Thanks for the input on separating Portal and Server.  I hadn't had the experience of support asking about rolling back to a snapshot before, hadn't occurred to me.