Spot instances are designed around fluctuating workloads with flexible start and end times. However, when used with automatic scaling, it can make it possible to replace On-Demand instances at a fraction of the cost.
Spot Instances Save about 50-70%
Spot Instances is a special type of EC2 instance that enables AWS to sell reserve composition capacity, often at large discounts. They can be terminated at any time by AWS, with two minutes notice, but the completion rate is quite low (less than 5% per month for most cases), and they are intended for use in an autoscaling group anyway.
In-house pricing was used to fluctuate during the day, much like a stock market, making it difficult to assess the total monthly cost of operating a fleet of spot-in-place that is always in place and causes to close quite often.
However, AWS fixed this problem in early 2018, and now location agencies look very different. Instead of offering extra computer capacity and letting society decide the price, AWS sets the price to the lowest value they are willing to sell their extra computer capacity.
This means that the pricing of on-site instances is quite consistent and that it lasts much longer. Most fluctuations occur during a month rather than independent daily peaks. Most cases, as
c5 series, stay pretty flat:
Some cases see almost no fluctuations, as
t3 series. You can see the current prices for spot instances from the EC2 console, under “Spot Requests”> “Pricing history”:
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On average, however, you can save at least 50% and up to about 70% for most of the latest instances. AWS claims that spot agencies can save “up to” 90%, but that’s mostly just marketing, as the only 90% savings are on older instance types that AWS rarely sells anymore.
It puts space conditions in a very useful place. They are about the same price as a 3-year reserved instance agreement without the obvious disadvantage of being locked into a 3-year contract.
Automatic scaling fixes disadvantages during instance steps
You would think that the large cost savings would be offset by another disadvantage, but that is certainly not the case in practice. The main problem with point instances is that they can be terminated at any time by AWS, with just two minutes notice. This sounds like a problem, but with automatic scaling the problem is minimized.
Automatic scaling is a feature of AWS that scales your server architecture to meet demand. If your web server becomes overloaded, a new one is created automatically to help balance the load. This requires you to automate the server’s life cycle, from installing packages to getting your code up and running, but it’s pretty easy to configure otherwise.
Auto Scaling attempts to maintain a target number of servers, and if one of your servers crashes, a replacement server may spin up. This also works for Spot instances – in the event that AWS regains computer capacity, a new Spot Instance can be created on the site. If you have multiple instances in an automatic scaling group, you will not experience any downtime. The time it takes to set up automatic scaling is the only downside of Spot Instances, but you only need to do it once to save lots of money each month on calculating costs.
With how large the location instances are, they make On-Demand look strange for expensive in comparison. Spot instances seem to be the real cost that AWS is willing to sell its instances at – they want you to adapt to their multi-server scalable service schedule, as it is better for both the company’s growth and AWS’s margins, and they use lower prices to entice you to set up automatic scaling. Auto-scaling itself also saves money, and in combination with Spot Instances makes running scalable workloads as web servers much cheaper than reserved instances.
Of course, if all you need is a single web server and want it to be available 100% of the time, it may make more sense to use a reserved instance (which saves a similar amount of money), rather than setting up an automatic scaling group. Spot instances are only worth it when you have more than one instance, otherwise you may experience a short downtime if AWS regains the instance.
How to work with automatic scaling
You can read our full guide on how to set up auto-scaling, but the essence of it is quite simple.
First, you need to find a way to automate the server life cycle. You will need to create a design script that can handle all the installation that you would normally do if you were to manually create a new server. It may take some time, but it guarantees that the scaling can be done automatically. To speed up the creation of new instances, create a custom AMI that contains all your pre-installed software (and even your own code, if you choose).
Then create a new boot configuration from the Automatic Scaling tab in the EC2 console. This configuration contains all the information about how to start servers in the Auto Scaling group, such as instance, images, and startup scripts. On the “Configure Detail” tab, select “Request Location Settings.”
Using Spot Instances in an autoscaling group does not have much disadvantage, unless your application really can not handle server-level interruptions. A good rule of thumb is that if your application can be easily balanced, it probably has no problem with Spot Instances.