Instance Families and Types

When you launch an instance, you specify the instance type. If you don't specify an instance type when you launch an instance, the default is an M1 Small (m1.small) instance.

*Instance store volumes may not be mounted by default. For more information, see Instance Store Device Names.

**The cg1.4xlarge instance type has 1 GiB reserved for GPU operation. The 21.5 GiB doesn't include the on-board memory of the GPUs, which is 3 GiB per GPU for the NVIDIA Tesla M2050. Before you launch your first cg1.4xlarge instance, complete the Amazon EC2 instance request form.

***The hi1.4xlarge instance type is based on solid-state drive (SSD) technology. For more information, see High I/O Instances.

An EBS-optimized instance uses an optimized configuration stack and provides additional, dedicated capacity for EBS I/O. This optimization provides the best performance for your EBS volumes by minimizing contention between EBS I/O and other traffic from your Amazon EC2 instance.

EBS optimization enables instances to fully utilize the IOPS provisioned on an EBS volume. EBS-optimized instances deliver dedicated throughput to EBS, with options between 500 Mbps and 1,000 Mbps, depending on the instance type you use. When attached to an EBS-optimized instance, Provisioned IOPS volumes are designed to deliver within 10 percent of their provisioned performance 99.9 percent of the time in a given year. For more information, see Provisioned IOPS Volumes.

The following instance types can be launched as EBS-optimized instances:

When you use an EBS-optimized instance, you pay an additional low, hourly fee for the dedicated capacity.

The following table lists the maximum number of Elastic Network Interfaces (ENI) per EC2 instance type and the maximum number of private IP addresses per ENI. ENIs and multiple private IP addresses are only available in EC2 instances running in Amazon Virtual Private Cloud. For more information, see Multiple IP Addresses.

Amazon EC2 instances can run Microsoft Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, or Windows Server 2012. The Windows AMIs provide you with all standard Windows Server functionality.

Using Amazon EC2 instances running Windows is similar to using instances running Linux/UNIX. The following are the major differences between instances that use Linux/UNIX and Windows:

Amazon EC2 currently provides the following Windows Server AMIs:

The Windows public AMIs that Amazon provides are unmodified versions of Windows with the following two exceptions: we added drivers to improve the networking and disk I/O performance and we created the Amazon EC2 configuration service. The Amazon EC2 configuration service performs the following functions:

For more information about the EC2 configuration service, see Using Ec2Config Service in the Microsoft Windows Guide.

Changing to a utility computing model changes how developers are trained to think about CPU resources. Instead of purchasing or leasing a particular processor to use for several months or years, you are renting capacity by the hour. Because Amazon EC2 is built on commodity hardware, over time there might be several different types of physical processors underlying different virtual EC2 instances. Our goal is to provide a consistent amount of CPU capacity regardless of the actual underlying hardware.

Amazon EC2 uses a variety of measures to provide each instance with a consistent and predictable amount of CPU capacity. To make it easy for developers to compare CPU capacity between different instance types, we defined an Amazon EC2 Compute Unit. One EC2 Compute Unit provides the equivalent CPU capacity of a 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor. This is also the equivalent to an early-2006 1.7 GHz Xeon processor referenced in our original documentation.

To find out which instance works best for your application, we recommend launching an instance and using your own benchmark application. This helps you determine which instance type works best for your specific use case.

Amazon EC2 provides virtualized server instances. Whereas some resources like CPU, memory, and instance storage are dedicated to a particular instance, other resources such as the network and the disk subsystem are shared among instances. If each instance on a physical host tries to use as much of one of these shared resources as possible, each receives an equal share of that resource. However, when a resource is under-utilized, you are often able to consume a higher share of that resource while it is available.

The different instance types provide higher or lower minimum performance from the shared resources depending on their size. Each of the instance types has an I/O performance indicator (low, moderate, high, etc.). Instance types with high I/O performance have a larger allocation of shared resources. Allocating a larger share of shared resources also reduces the variance of I/O performance. For most applications, moderate I/O performance is more than enough. However, for applications that require greater or more consistent I/O performance, consider instances with higher I/O performance.

To help categorize and manage your instances, you can assign tags of your choice to them. For more information, see Tagging Your Amazon EC2 Resources.