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When the AWS C4 instances became available in January, IT pros who used C3 machines attached to the Elastic Block Store (EBS) without local disk expected the new instance type to deliver cost savings. AWS C4 instances are EBS-attached by default, and thus won't waste local drive capacity.
However, in absolute terms, the AWS C4 instances are priced higher than their C3 counterparts. For example, the C4.large and C3.large both offer two CPU cores and 3.75 GB of memory. But the C4.large instance on demand costs $0.116 per hour for Linux and $0.199 per hour for Windows, while the C3.large costs $0.105 hourly for Linux and $0.188 hourly for Windows. There is a slight uptick in Elastic Compute Units (ECU), an Amazon-specific measure of CPU power; the C4.large has 8 ECU while the C3.large has 7 ECU.
Kevin FelichkoCTO, PropertyRoom
The IT team at PropertyRoom.com, an online auction company based in Frederick, Md., tested C3.large and C4.large instances using Tsung, an open source load testing tool. The team saw a 30% increase in the average page response time moving from C3 to C4. The C4 instance was also able to handle 20% more requests over a five-minute period than the C3 instance.
"That's not bad for a minor increase in the on-demand pricing, around $8 per month," said Kevin Felichko, PropertyRoom's CTO. The company plans to put C4s into production to run its auction platform.
Others say the higher price isn't worth it for the typical AWS customer who doesn't max out the CPU power of the C3 line.
"The improved dedicated EBS throughput could be attractive for CPU-intensive applications, but none of my current clients have that need," said Mark Szynaka, a cloud architect for CloudeBroker, based in New York. "The C4 instances … will be beneficial for heavy data analytics, but I don't think it will cannibalize a large percentage of their C3 product offerings."
Ultimately, the suitability of AWS C4 instances depends on the specific workload being deployed on them.
"Our financial clients are very interested in the C4 instances," said Eric Dynowski, CEO and co-founder of the Turing Group, a cloud consulting and managed services firm based in Evanston, Ill. "They are all about maximizing performance and less concerned with [spending]."
The current M, R and C3 instances meet most other clients' needs, Dynowski said.
For now, this means AWS C4s aren't replacing C3s wholesale, according to AWS software partners who are tracking customers' usage of the new instances.
Cloudability, Inc., for example, has seen a "very small percentage" of its customers move to C4s so far, according to Toban Zolman, the company's vice president of product development.
That's not to say an organic transition to the AWS C4 instances won't happen over time, Zolman added. Adoption of new instances tends to happen this way, with a small immediate bump in usage followed by a long process of cutting over to the latest instances as new applications come online, he said.