Something to inform people that you're resetting the servers. Make be make the text red.
The typical "Servers will be shutting down in 30s. Please move to a safe location and log off"
"Servers will be shutting down in 20s. Please move to a safe location and log off"
"Servers will be shutting down in 10s. Please move to a safe location and log off"
"Servers will be shutting down in 5s. Please move to a safe location and log off"
"Servers is shutting down. If you see this message, you suck at following instructions"
#System wide messaging system
hidden saddle
wet mauve
While the servers are in a sort of unstable state, it might be good to have a nightly/morningly outage, where you reset them.
Like Dream is saying, maybe push a warning out 5-10 minutes before, then like a minute before, then "Servers is shutting down. If you see this message, you suck at following instructions"