Compute Optimized Instances

Compute optimized instances are ideal for compute-bound applications that benefit from high performance processors. They are well suited for the following applications:

Batch processing workloads
Media transcoding
High-traffic web servers, massively multiplayer online (MMO) gaming servers, and ad serving engines
High performance computing (HPC) and other compute-intensive applications

Contents

Hardware Specifications
Compute Instance Performance
Compute Instance Features
Support for 36 vCPUs
Instance Limits

Hardware Specifications

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

Compute Instance Performance

EBS-optimized instances enable you to get consistently high performance for your EBS volumes by eliminating contention between Amazon EBS I/O and other network traffic from your instance. C4 instances are EBS-optimized by default at no additional cost. You can enable EBS optimization for your C3 instances for an additional low, hourly fee. For more information, see Amazon EBS–Optimized Instances.

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.

The c4.8xlarge instance type provides the ability to control processor C-states and P-states on Linux. C-states control the sleep levels that a core can enter when it is inactive, while P-states control the desired performance (in CPU frequency) from a core. For more information, see Processor State Control for Your EC2 Instance.

Compute Instance Features

The following is a summary of features for compute optimized instances:

	VPC only	EBS only	SSD volumes	Placement group	HVM only	Enhanced networking
C3			Yes	Yes		Intel 82599 VF
C4	Yes	Yes		Yes	Yes	Intel 82599 VF

For more information, see the following:

Support for 36 vCPUs

The c4.8xlarge instance type provides 36 vCPUs, which might cause launch issues in some Linux operating systems that have a vCPU limit of 32. We strongly recommend that you use the latest AMIs when you launch c4.8xlarge instances.

The following AMIs support launching c4.8xlarge instances with 36 vCPUs:

Amazon Linux AMI 2017.03 (HVM)
Ubuntu Server 14.04 LTS (HVM)
Red Hat Enterprise Linux 7.1 (HVM)
SUSE Linux Enterprise Server 12 (HVM)

If you must use a different AMI for your application, and your c4.8xlarge instance launch does not complete successfully (for example, if your instance status changes to stopped during launch with a Client.InstanceInitiatedShutdown state transition reason), modify your instance as described in the following procedure to support more than 32 vCPUs so that you can use the c4.8xlarge instance type.

To update an instance to support more than 32 vCPUs

Launch a C4 instance using your AMI, choosing any C4 instance type other than c4.8xlarge.
Update the kernel to the latest version by following your operating system-specific instructions. For example, for RHEL 6, use the following command.
```
Copy
sudo yum update -y kernel
```
Stop the instance.
(Optional) Create an AMI from the instance that you can use to launch any additional c4.8xlarge instances that you need in the future.
Change the instance type of your stopped instance to c4.8xlarge (choose Actions, Instance Settings, Change Instance Type, and then follow the directions).
Start the instance. If the instance launches properly, you are done. If the instance still does not boot properly, proceed to the next step.
(Optional) If the instance still does not boot properly, the kernel on your instance may not support more than 32 vCPUs. However, you may be able to boot the instance if you limit the vCPUs.
1. Change the instance type of your stopped instance to any C4 instance type other than c4.8xlarge (choose Actions, Instance Settings, Change Instance Type, and then follow the directions).
2. Add the maxcpus=32 option to your boot kernel parameters by following your operating system-specific instructions. For example, for RHEL 6, edit the /boot/grub/menu.lst file and add the following option to the most recent and active kernel entry:
```
Copy
default=0
timeout=1
splashimage=(hd0,0)/boot/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux Server (2.6.32-504.3.3.el6.x86_64)
root (hd0,0)
kernel /boot/vmlinuz-2.6.32-504.3.3.el6.x86_64 maxcpus=32 console=ttyS0 ro root=UUID=9996863e-b964-47d3-a33b-3920974fdbd9 rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us LANG=en_US.UTF-8 xen_blkfront.sda_is_xvda=1 console=ttyS0,115200n8 console=tty0 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_NO_LVM rd_NO_DM
initrd /boot/initramfs-2.6.32-504.3.3.el6.x86_64.img
```
3. Stop the instance.
4. (Optional) Create an AMI from the instance that you can use to launch any additional c4.8xlarge instances that you need in the future.
5. Change the instance type of your stopped instance to c4.8xlarge (choose Actions, Instance Settings, Change Instance Type, and then follow the directions).
6. Start the instance.

Instance Limits

C4 instances require 64-bit HVM AMIs. They have high-memory (up to 60 GiB of RAM), and require a 64-bit operating system to take advantage of that capacity. HVM AMIs provide superior performance in comparison to paravirtual (PV) AMIs on high-memory instance types. In addition, you must use an HVM AMI to take advantage of enhanced networking.
There is a limit on the total number of instances that you can launch in a region, and there are additional limits on some instance types. For more information, see How many instances can I run in Amazon EC2?. To request a limit increase, use the Amazon EC2 Instance Request Form.

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