I have several Windows ec2 instances that are controlled by an ELB (Elastic Load Balancer). These instances are scheduled to install any new windows updates once per day during non-peak hours.
Automatically installing Windows updates often causes all of my Windows ec2 instances to be unavailable at the same time. Service availability is one of the primary reasons that I am using an ELB.
How can I install Windows updates automatically and prevent service disruption due to installing those updates?
Edit: I want to do this without the overhead of running an additional service (e.g. WSUS or a domain controller).