We are currently working on upgrading our Production ArcGIS Server 10.3.1 windows operating system from 2008 to 2012 and we would like to know if anyone has any helpful tips on this transition that will minimize downtime. Our plan thus far is the following and any helpful tips would be great. We have just moved our sql databases onto their own server separate from the ArcGIS server so the data will still be accessible from any ArcGIS server that we stand up. Our process that we are thinking is as follows, let me know if others think this will work or if there is a better way.
1. Upgrade a development server to Windows 2012.
2. Mirror production server on development so that data accessed that does not come from sql databases will be accessed even if production is down.
3. Set service .mxd's that reference file geodatabases to relative path.
4. Export Site from production through ArcGIS server admin
5. Import site from previous backup onto the development server.
6. Copy cache directories from production to development server.
7. Setup 1 A-Name to 2 IP addresses in DNS so Web Adaptor will still recognize development as production.
8. Shut down production and see if everything works, if not bring production back up and re-think our process.
9. Use development as production while the production server is rebuilt.
Let me know if anyone can see something that we may be missing or will not work!