Amazon has scheduled a massive reboot of servers affecting hundreds or possibly thousands of applications running on its AWS EC2 cloud, says cloud consultant Rand Bias at the Cloudscaling blog.

Bias has come upon an e-mail he says was sent to EC2 customers. "One or more of your Amazon EC2 instances have been scheduled for a reboot in order to receive some patch updates. Most reboots complete within minutes, depending on your instance configuration," it says.

Speculation is that the reboot involves security patches to the underlying servers hosting the Amazon applications.

Amazon is constantly patching and updating service. But such updates don't typically knock applications offline, even for the duration of a reboot. An Amazon spokesperson downplayed the impact, saying that customers were simply being informed of scheduled maintenance, GigaOM reports. Amazon also gives customers the option of doing their own reboots, it says.

A check of the Amazon Dashboard at 4:46 pacific does show problems with "ELB scaling and provisioning in the US-EAST-1 region" which is served through the North Virginia data center. This was the data center responsible for the big Amazon outage in the spring.

Users of Amazon's cloud service seem none too happy with their applications being taken offline. Says William Vambenepe on Twitter: "Today is apparently EC2-reboot-Wednesday. Also know as the day some CIOs learn that (1) they use EC2 and (2) they're not using it very well."