Andrew Nhem - February 26, 2017

Cost efficiency with I3 I/O-optimized EC2 instances

AWS announced a new addition to its I/O-optimized EC2 instance fleet: the I3. We’ll explore what these new instances deliver and how much more cloud cost-efficient they are compared to the previous generation.

AWS announced a new addition to its I/O-optimized EC2 instance fleet: the I3. We’ll explore what these new instances deliver and how much more cost-efficient they are compared to the previous generation.

Could the new I3s be right for your disk I/O-heavy workloads? Let’s take a look.

How does this impact AWS EC2 cost efficiency?

Using a quick analysis of a sample segment and snapshot from our own customer base from January 2017, nearly 50% of their AWS costs came from EC2. Of those EC2 costs, 3% came from I2 instances. If these customers were to migrate their I2s to I3s, they could save approximately 60% of their I/O-intense instance costs.

Let’s go through a scenario using this customer segment data and Linux On-Demand hours. If this sample segment of customers spends about $1.2 million a month on I2s, switching to I3s can lower costs by $725,000 per month. Of course, there are many considerations and concerns when migrating between EC2 instances, but we use these figures to illustrate the immediate potential from an AWS cost efficiency perspective.

Let’s break down what the I3s deliver in terms of processing and storage.

What’s new with the EC2 I3 instance type?

The I3s are the newest member of AWS’s disk I/O-optimized lineup. They feature high-frequency (2.3GHz) Intel Xeon E5-2686 v4 (Broadwell) processors, NVMe SSD storage capable of 3.3 million IOPS in 4 KB blocks, up to 16 GB/second of sequential disk throughput and enhanced networking capabilities like the throughputs we’re seeing on the M4, X1 and other recent AWS EC2 updates.

With greatly improved storage density, increased sequential read and write speeds and faster CPUs at the helm, these instances are aligning increased IOPS, computing power, and network speed for your disk I/O-intense jobs. According to AWS, this IOPS-intense capability is ideal for running workloads such as NoSQL databases (e.g., Cassandra, MongoDB, Redis), in-memory databases, transactional databases at scale, big data warehousing, Elasticsearch and enterprise-level analytics workloads.

Specs and pricing: I3s deliver more for less

AWS packs computing power and dense NVMe SSD storage into an affordable package when compared to the previous generation. The I3s also make high I/O instances more available and scalable by including large and 16xlarge sizes. The previous I2 instances were only available in sizes between xlarge and 8xlarge.

We’ll compare the i3.4xlarge with the i2.4xlarge to show the difference in specs and value:

Instance vCPU Memory (GB) Storage (TB) Linux On-Demand Pricing
i3.4xlarge 16 122 GB 3.8 TB (2 disks) $1.248 per hour
i2.4xlarge 16 122 GB 3.2 TB (4 x 800GB SSDs) $3.410 per hour


Instance Price per vCPU per hour Price per storage TB per hour
i3.4xlarge $0.010 per vCPU per hour $0.328 per TB per hour
i2.4xlarge $0.213 per vCPU per hour $1.056 per TB per hour


Not only does the i3.4xlarge deliver a cheaper rate for better processors than the i2.4xlarge, but it also features more NMVe SSD storage at a much cheaper rate. This pattern occurs when comparing the other instance sizes between generations. We’re seeing about a 63% savings on average when comparing the two generations.

What to consider before migrating

On paper, the I3s seem like a solid upgrade for many I2 users —who wouldn’t want better processors and incredibly fast NVMe SSD access? We asked a few of our engineers about what they’d look out for when considering migrating from the I2 to I3 instances. We’ll go through a few of their responses below.

I3 instances are VPC-only

Our engineers pointed out that the I3 instances require running Amazon Machine Images (AMIs) on a Virtual Private Cloud (VPC). For EC2 classic users on I2s, there’s a bit more consideration about what moving to VPC could mean to your infrastructure. AWS provides a thorough list of compatible AMIs in their release article:

  • Amazon Linux AMI
  • RHEL – 6.5 or better
  • CentOS – 7.0 or better
  • Ubuntu – 16.04 or 16.10
  • SUSE 12
  • SUSE 11 with SP3
  • Windows Server 2008 R2, 2012 R2, and 2016

Different instances require new reservations

Current I2 users should take a look at their current Reserved Instance portfolios and consider what to do with reserved hours remaining for their I2 instances. Migrating to I3s means cheaper rates in comparison, but those savings can easily be negated if there are reserved I2 hours sitting unused (this can get even worse if these hours were prepaid for on a long three-year term!).

While we did an On-demand comparison above, any team wanting to migrate over to I3s that also has I2s on reserved hours should take all reserved hours into consideration to determine exact costs and/or savings. Pro-tip: Cloudability users can put our RI planner to work to make sure all bases are covered.

Big architecture changes, like the release of I3 instances and the potential for big savings upon migration, promote the use case for Convertible RIs. This RI type delivers more flexibility for AWS users and takes advantage of instance updates, letting Convertible RI users exchange existing RIs on the I2s for a newer reservation of hours on I3 instances. We cover this in greater detail in a previous article on Convertible RIs and our RI planner, so check that piece out to learn more.

Get the most value out of EC2 with every AWS upgrade

As AWS continues to improve each of their EC2 instance types, it’s a new opportunity for users to capture even more cloud compute value. The new I3s don’t just mean better processors and storage types and speeds. It means accessing cloud compute resources that can prepare your business to tackle new levels of scale and success.

Using a cloud cost management tool like Cloudability ensures that potential I3 purchases deliver the most value possible. Tracking cost and usage data in by key reports and widgets lets you know that every EC2 hour is put to use. It lets you find waste before it makes a big impact on your bill, and plan out efficient EC2 infrastructures that can make the most of additional savings tactics like Reserved and Spot Instances.

See your EC2 cost and usage data in a whole new light by checking out a free trial today, or by getting in touch with one of our EC2 experts.

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