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Cost Optimization

AWS c4: is the power worth the price?

By Leah Weitz on January 13, 2015

If you’re like us, you’ve been looking forward to the release of Amazon’s new c4 instance type ever since it was pre-announced in November—and today, the wait is over. Now that the latest generation of compute-optimized instances has arrived, it’s time to decide: are the c4’s bump in power worth the bump in price?

The price of efficiency

C4 instances run on Intel Xeon E5-2666 v3 processors, specifically designed by Intel for running EC2. They’ve got the highest performing processors in EC2; however, they’re also more expensive.

AWS c3 and c4 pricing

These custom processors allow for an improved price/compute performance over c3, but come at a 10% increase in cost (when comparing c3.2xlarge to c4.2xlarge). Whether they’re worth the 10% bump will depend on two things: how much you save on EBS Optimization, which is enabled at no extra charge for all c4 instances, and how the improved performance impacts your workload efficiency.

Download the guide: Choosing the right EC2 instances

If you’re paying a lot for EBS Optimization on c3, a change to c4 might represent a source of hidden savings that would help to justify the move. You might also find that the improved performance allows you to run more workloads and increase your output accordingly; if the ability to do so will make you more money than the bump in price will cost you, then changing from c3 to c4 makes sense.

One way to determine the precise impact that the improved compute performance will have is by trying it. You can do so by spinning up a c4 instance and running an equal workload to one of your c3s, then comparing output.

Aside from the improved compute performance, c4 instances only differ from c3 in memory and storage options. C4 offers a 11% increase in ECU and is EBS only, whereas c3 uses SSD.

Making the jump

If you determine that moving to c4 will be a cost-effective change, you’ll want to ensure that you time the move right. It can be tempting to go all-in right off the bat, but such a drastic change has its own cost implications—and can easily endanger any savings you might garner from c4’s improved price/compute rate.

As a more moderate route, you can phase in c4 instances as you start new projects or rotate your infrastructure. But if you’re averse to waiting that long, just be sure to calculate your gains/losses accordingly.

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