As part of the continuing server upgrade saga, I need to upgrade the operating system on the current server, which is still running Debian 8. I'll be taking the game server down later tonight (see subject for the exact time), do the upgrade and reboot. Nominally, it should be done in less than an hour, but you never know what extra peculiarities might arise along with an upgrade, so I can't really give an exact time estimate.
As for the upgraded server, I've just ordered and set up the hardware, but I'm still playing around a bit with the new storage stack, parts of which I haven't used previously, so I'm not entirely ready to move the server over yet. I'm not exactly sure when I do the actual transfer, or how it interacts with the weekly patch, but judging from the previous move of Moltke (see the link above), I expect it to take at least 5-6 hours to complete, during which the game will have to be down, and during at least part of which the forums also have to stay down. I expect to do it on Wednesday at the latest, but I'll keep you updated.