AWS Reserved instances and Availability zones for Elastic Beanstalk

Question

As I understand in order to take advantage of reserved instance pricing, the AZ of the reserved instance must match the AZ of my Elastic Beanstalk's EC2 instance.

In order to achieve this I figure I would need to limit my EB app to just one availability zone. This would guarantee my main instance is running in the discounted AZ.

But by doing this additional instances would also be locked into this zone potentially reducing availability.

Are these assumptions correct? And if so how can I work around them so that my main instance is always in the discounted zone, and additional instances can be in another zone?

Answer 1

You assumptions are right.

Reserved instances are bound to the availability zone (though they recently started allowing the AZ modification before the tenure expiry - http://aws.amazon.com/about-aws/whats-new/2013/09/11/amazon-ec2-now-offers-reserved-instance-modifications/).

The only thing you can ensure is that out of the many AZ which you choose in beanstalk, keep them as much same as the Reserved instances. In AWS words "If you purchased Reserved Instances, you need to specify the same Availability Zone(s) that you specified when you purchased your Reserved Instances" http://docs.aws.amazon.com/elasticbeanstalk/latest/dg/using-features.managing.as.html

Answer 2

Are you could buy two RI and put them in two different AZ and limit your EB to those two AZ then at least you have some redundancy.