I have an Octopus deployed Umbraco site which can take a very long time to respond when deployed to QA, but responds very quickly when deploying to UAT.
Both servers are built the same using Chef, but had one patch applied which we're currently rolling back to be the same at UAT.
On the QA server, a bunch Razor gets compiled under C:\windows...\Temporary ASP.NET Files\root... and looking at the timestamps, it can take close to 15 minutes. On the UAT server, those same files have timestamps within a minute.
I did a diff on those directories, and the files are (generally) the same other than some unique identifiers.
Some QA files:
Some UAT files:
While waiting for the site to come up, there's always some disk activity in Resource Monitor doing something in Temp ASP.NET: