I received this message yesterday from our hosting provider:
Between 12:30am and 4am local time for your service on Wednesday, December 16, we plan to gracefully shut down your VDS, upgrade the machine hosting it to an updated version of Xen/Linux, reboot it, and bring your VDS back online. We expect for this process to cause approximately 30-60 minutes of downtime for your service.
Because this maintenance will require a full reboot, we recommend that you configure any services which need to always be running to start automatically when the VDS is booted.
We do not anticipate problems due to this update, but to be safe, we recommend that you externally back up any critical (irreplaceable) files before the maintenance event and before any other service adjustment.
This Xen upgrade is required because of an important Xen vulnerability. We are rebooting all of our VDS-hosting machines the same morning.
Update on 12/15: Please note that Windows 2012 R2 still has a problem that causes VDSes running that OS to not always successfully boot. Our system attempts to detect this and reboot those servers again, but after multiple attempts, Windows will go to a recovery screen. If this happens to you, then you will need to use the VNC console to tell Windows to restart again.
The downtime that we will experience will affect all of our game servers, as well as these forums. It is possible that the forums and game servers will experience outages at different times, as they are hosted on different machines.
The downtime is scheduled to take place 03:30 through 07:00 EST.