I received notification that many of my EC2 instances will be rebooted for scheduled maintenance. They are scheduled for an "instance-reboot," which makes sense because most of my instances are S3 backed. However, I have EBS instances that are schedule for an "instance-reboot" as well. It was my understanding that EBS instances are self contained because they are on EBS backed storage. That said, why do my EBS instances require a "instance-reboot"?
Amazon is upgrading EC2, and as such many EC2 instances must be rebooted, hence the "instance-reboot" status. You can reboot these instances yourself on your own schedule, or wait for the scheduled task to run. The reboot has nothing to do with the storage engine, but more about the kernels that are backing the virtual machines.