Menu
Amazon Elastic Compute Cloud
User Guide for Linux Instances

I2 Instances

I2 instances are optimized to deliver tens of thousands of low-latency, random I/O operations per second (IOPS) to applications. They are well suited for the following scenarios:

  • NoSQL databases (for example, Cassandra and MongoDB)

  • Clustered databases

  • Online transaction processing (OLTP) systems

Hardware Specifications

For more information about the hardware specifications for each Amazon EC2 instance type, see Amazon EC2 Instances.

I2 Instance Features

The following is a summary of the features for I2 instances:

  • The primary data storage is SSD-based instance storage. Like all instance storage, these volumes persist only for the life of the instance. When you stop or terminate an instance, the applications and data in its instance store are erased. We recommend that you regularly back up or replicate the data that you've stored in instance storage. For more information, see SSD Instance Store Volumes.

  • You can enable enhanced networking capabilities. Enhanced networking provides significantly higher packet per second (PPS) performance, lower network jitter, and lower latencies. For more information, see Enhanced Networking on Linux.

  • You can cluster I2 instances in a placement group. Placement groups provide low latency and high-bandwidth connectivity between the instances within a single Availability Zone. For more information, see Placement Groups.

  • You can enable EBS–optimization to obtain additional, dedicated capacity for Amazon EBS I/O. For more information, see Amazon EBS–Optimized Instances.

I2 Instance Requirements

The following are the requirements for I2 instances:

  • You must launch an I2 instance using an HVM AMI.

  • To ensure the best IOPS performance from your instance on Linux, we recommend that you use the most recent version of the Amazon Linux AMI, or another Linux AMI with a kernel version of 3.8 or later. If you do not use a Linux AMI with a kernel version of 3.8 or later, your instance will not achieve the maximum IOPS performance available for this instance type. For more information, see SSD I/O Performance.

  • There is a limit on the total number of instances that you can launch in a region, and there are additional limits on some I2 instance types. For more information, see How many instances can I run in Amazon EC2?

    If you need more I2 instances, you can request them using the Amazon EC2 Instance Request Form.

SSD I/O Performance

If you use a Linux AMI with kernel version 3.8 or later and utilize all the SSD-based instance store volumes available to the instance, you can get at least the minimum random IOPS (4,096 byte block size) listed in the following table. Otherwise, you'll get lower IOPS performance than what is shown in the table.

Instance SizeRead IOPSFirst Write IOPS

i2.xlarge

35,000

35,000

i2.2xlarge

75,000

75,000

i2.4xlarge

175,000

155,000

i2.8xlarge

365,000

315,000

As you fill the SSD-based instance storage for your instance, the number of write IOPS that you can achieve decreases. This is due to the extra work the SSD controller must do to find available space, rewrite existing data, and erase unused space so that it can be rewritten. This process of garbage collection results in internal write amplification to the SSD, expressed as the ratio of SSD write operations to user write operations. This decrease in performance is even larger if the write operations are not in multiples of 4,096 bytes or not aligned to a 4,096-byte boundary. If you write a smaller amount of bytes or bytes that are not aligned, the SSD controller must read the surrounding data and store the result in a new location. This pattern results in significantly increased write amplification, increased latency, and dramatically reduced I/O performance.

SSD controllers can use several strategies to reduce the impact of write amplification. One such strategy is to reserve space in the SSD instance storage so that the controller can more efficiently manage the space available for write operations. This is called over-provisioning. The SSD-based instance store volumes provided to an I2 instance don't have any space reserved for over-provisioning. To reduce write amplification, you should leave 10% of the volume unpartitioned so that the SSD controller can use it for over-provisioning. This decreases the storage that you can use, but increases performance.

I2 instance store–backed volumes support TRIM. You can use the TRIM command to notify the SSD controller whenever you no longer need data that you've written. This provides the controller with more free space, which can reduce write amplification and increase performance. For more information, see Instance Store Volume TRIM Support.