Joe,

What I have done for this situation is to create a new page, set it visible to all, and put HTML on it with the message about site being down.

Then in Admin --> Site Settings, make this page the Home page.

Using your Admin --> Pages menu, now make settings for every other page as visible to Admin only. Change them back when you are finished.

I briefly considered that, but this site has dozens of pages, divided up among about 8 different possible security roles, and it was a really complicated process to get all the permissions set up this way the first time, and I'm reluctant to change all that for what I hope is a 30-45 minute outage while I upgrade.

Also, since requests are still being handled by DNN, won't I still run into the possibility that someone else will see the automated upgrade page instead of me after I've uploaded the DLLs?  Also, since it's going to take a while to get all these files up, what's to stop the upgrade from trying to start even when it doesn't have all the files yet?  I've seen a lot of reports around here about upgrades failing; is it possible that upgrades are failing because the upgrade started too soon, or one of someone's users started the upgrade without them?

Originally I wanted to upgrade on an offline server, then redirect all requests to that server only while I upgraded the other one.  However, it looks like two versions of DNN can't run against the same database, right?

Sorry for all the questions, but I got handed this project and before two months ago, I had had zero exposure to DNN, and this is a fairly complicated implementation, I think.