The datacentre will be rebooting your server in order to install to a new kernel. Total downtime is expected to be about ten minutes during the maintenance window:
Start: Saturday, May 5, 2012 1:00AM CDT (2:00 PM, SGT)
End: Saturday, May 5, 2012 2:00AM CDT (3:00PM, SGT)
This new kernel provides enhanced security updates and server performance upgrades and is necessary to continue operating the server at peak performance levels.