Using reserved instances in the elastic bean stack balancer

Question

I run the application with an elastic balancing balancer throughout the year. I am looking for ways to cut costs and found that I could potentially use the reserved ec2 instances instead of the On-Demand instances we are currently using. My load balancer is currently using two instances.

I want to make a switch, but I'm not sure how this process really works. I want everything to be clear before doing anything.

From my point of view, if I reserve two instances of the same type as in my application (t2.large with Linux) for the same availability zones (1 in eu-west1b, the other in eu-west1c), I could use these instances for load balancing. Will the instances of the same type that I just deployed immediately fall under the norms of the reserved instance? Should I rebuild the environment and create two new instances that match the reserved ones?

Answer 1

A Reserved Instance - A prepayment method for Amazon EC2 capacity.

If you were to buy two reserved instances (in your case, 2 x t2.large Linux), then for each hour of the year, while the reserved instance is valid, you will have the right to run the corresponding types of instances (2x t2.large Linux) without an hourly fee .

There is no need to identify which instance is a reserved instance. Rather, the billing system will select the appropriate instance that runs every hour and will not pay hourly charges.

Therefore, if you use only the corresponding instances , they will (by default) be identified as reserved instances and will not receive hourly payments. However, if you run other instances, there is no way to control which instance gets a price advantage.

You can purchase a reserved instance with or without access zone identification. If AZ is selected, then the price benefit of the reserved instance corresponds only to the instance running in this AZ, and there is also a capacity reservation to give you priority when launching the instances corresponding to the Reserved instance. If AZ is not selected, then the price advantage extends to all instances launched in this region, but there is no capacity reservation.

Bottom line: Yes, it will be applied immediately (for the number of instances for which you purchased reserved instances). There is no need to start / stop / restore anything.

Answer 2

For those looking for some certainty than John's (correct) answer, here are the official AWS documenting this:

In this case, you have a valid On Demand (T2) instance in your account for which you are currently paying on demand bids. You acquire a Reserved Instance that matches the attributes of your executable instance and a payment reward applies immediately. You then acquire a reserved instance for the C4 instance. You do not have any running instances in your account matching the attributes of this reserved instance. In the last step, you start the instance that matches the attributes of the C4 Reserved instance, and the payment reward is applied immediately.

From here: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-reserved-instances.html