I’ve been seeing this error on my TMG 2010 Standard server ever since I put it into production and I couldn’t understand what it was or why it was happening
I never understood this message because I’m running Standard edition, which doesn’t do arrays (you need Enterprise). I’ve also never configured any array settings, and I’ve never seen any array settings on the Standard edition that could be configured.
It turns out that even though this is Standard edition, and there are no array, TMG seems to still think of itself as being in an “array of one”. When I built the server it had a temporary IP address that was changed when I switched over from the old Firewall server. It is this change of IP address that caused the error. It never seems to have caused any problems that I noticed, so I ignored it.
As part of the “big recovery” I decided to kill all annoying errors. And this TechNet post had the solution.