Upgrading from 10.1.1 to 10.2.1

[TimHayes]

In the past with most ArcGIS for Server Upgrades you needed to completely uninstall the previous versions, loosing all your services and customizations. Then, starting from scratch, install the new version and have to spend hours and hours re-do all your services and customizations. I hope ESRI has finally created a way where upgrades simply overwrite previous versions leaving everything done previously intact.

When upgrading from ArcGIS for Server 10.1.1 to 10.2.1 will I need to uninstall 10.1.1?

Will I have to re-add services to Manager? I have some services that use Caching, will I need to re-do the Map Caching Scales?

I use ArcSDE/SQL Server Express 2008 R2 for Geodatabases, is there anything that will negatively impact these if I upgrade? something I should know beforehand?

Where can I find some good info on upgrading ArcGIS for Server 10.1.1 to 10.2.1?

[WilliamCraft]

In the past with most ArcGIS for Server Upgrades you needed to completely uninstall the previous versions, loosing all your services and customizations. Then, starting from scratch, install the new version and have to spend hours and hours re-do all your services and customizations. I hope ESRI has finally created a way where upgrades simply overwrite previous versions leaving everything done previously intact.

When upgrading from ArcGIS for Server 10.1.1 to 10.2.1 will I need to uninstall 10.1.1?

Will I have to re-add services to Manager? I have some services that use Caching, will I need to re-do the Map Caching Scales?

I use ArcSDE/SQL Server Express 2008 R2 for Geodatabases, is there anything that will negatively impact these if I upgrade? something I should know beforehand?

Where can I find some good info on upgrading ArcGIS for Server 10.1.1 to 10.2.1?

Upgrade paths for the Esri stack should proceed in the following order for the major components: Server first, clients second, geodatabase third. 

Beginning at 10.2, you'll be able to install newer versions of the software on top of the existing 10.2 installation.  In the case you are describing, you won't be able to install 10.2.1 on top of 10.1.1; instead, you will need to uninstall 10.1.1 first.  Whatever customizations you have made will need to be installed/configured again unfortunately.  For the services, you might be able to open your service definition (SD) files after 10.2.1 is installed and re-save them as 10.2.1 SD files, but the downside is that you will still need to re-create your services and all of their parameters.  In the past, whenever I've had to replace a server, I've been able to simply copy the service configuration files from one machine to another but in that case I was using the same version of ArcGIS on the new machine.  In your case, you are keeping the same machine and changing versions entirely so I don't know how well it would go to try and re-use your 10.1.1 service configuration files with 10.2.1.  Your caches might be ok to stay intact; make a backup of the cache directories and files and copy them back to the same location once the installation is complete.  You'll just need to set your cached services to Cached and point them at the tiles when you re-create the services.  Try that first; if it doesn't work then you'll have to re-cache.  Your map documents (the things you used to create your SDs) for your map services can be re-used though; just open and re-save them in 10.2.1 first as I think that is best practice. 

The geodatabase will not need an upgrade and neither will your ArcSDE command line tools; but if you do decide to upgrade those then upgrade your geodatabase last though, so that any older clients can still connect to the geodatabase as long as possible.  Newer geodatabases won't generally allow older clients to connect but Esri has a matrix they publish which shows connectivity compatibility between GDB and client.  Just remember to re-register your geodatabase as a data store with your new 10.2.1 installation of ArcGIS for Server.

EDIT: Apparently for ArcGIS Server, Esri states that an "in-place migration is more feasible when moving from 10.1 to 10.2.1 because you are not required to uninstall 10.1. However, the migrated site should still be thoroughly tested before being exposed to end users".  So, it might be ok after all to perform the 10.2.1 installation on top of your 10.1.1 installation; however from my experience I wouldn't recommend doing that.  I've had much better luck uninstalling and re-installing Esri software than performing upgrades.  It's more work, sure, but it saves more headaches and 2-hour phone calls with Tech Support, in my opinion.  In any event, below is the upgrade documentation from Esri (I'm assuming you have a Windows environment for AGS):

http://resources.arcgis.com/en/help/main/10.2/index.html#//0154000002p0000000