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-performance web servers

• High-performance computing (HPC)

• Scientific modeling

• Dedicated gaming servers and ad serving engines

• Machine learning inference and other compute-intensive applications

For more information, see Amazon EC2 C5 Instances.

Hardware Specifications

The following is a summary of the hardware specifications for compute optimized instances.

Instance type	Default vCPUs	Memory (GiB)
c4.large	2	3.75
c4.xlarge	4	7.5
c4.2xlarge	8	15
c4.4xlarge	16	30
c4.8xlarge	36	60
c5.large	2	4
c5.xlarge	4	8
c5.2xlarge	8	16
c5.4xlarge	16	32
c5.9xlarge	36	72
c5.12xlarge	48	96
c5.18xlarge	72	144
c5.24large	96	192
c5.metal	96	192
c5d.large	2	4
c5d.xlarge	4	8
c5d.2xlarge	8	16
c5d.4xlarge	16	32
c5d.9xlarge	36	72
c5d.12xlarge	48	96
c5d.18xlarge	72	144
c5d.24large	96	192
c5d.metal	96	192
c5n.large	2	5.25
c5n.xlarge	4	10.5
c5n.2xlarge	8	21
c5n.4xlarge	16	42
c5n.9xlarge	36	96
c5n.18xlarge	72	192
c5n.metal	72	192

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

For more information about specifying CPU options, see Optimizing CPU Options.

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. Some compute optimized instances are EBS-optimized by default at no additional cost. For more information, see Amazon EBS–Optimized Instances.

Some compute optimized instance types provide 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.

Network Performance

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

Instance types that use the Elastic Network Adapter (ENA) for enhanced networking deliver high packet per second performance with consistently low latencies. Most applications do not consistently need a high level of network performance, but can benefit from having access to increased bandwidth when they send or receive data. Instance sizes that use the ENA and are documented with network performance of "Up to 10 Gbps" or "Up to 25 Gbps" use a network I/O credit mechanism to allocate network bandwidth to instances based on average bandwidth utilization. These instances accrue credits when their network bandwidth is below their baseline limits, and can use these credits when they perform network data transfers.

The following is a summary of network performance for compute optimized instances that support enhanced networking.

Instance type	Network performance	Enhanced networking
c5.4xlarge and smaller | c5d.4xlarge and smaller	Up to 10 Gbps	ENA
c5.9xlarge | c5d.9xlarge	10 Gbps	ENA
c5.12xlarge | c5d.12xlarge	12 Gbps	ENA
c5n.4xlarge and smaller	Up to 25 Gbps	ENA
c5.18xlarge | c5.24xlarge | c5.metal | c5d.18xlarge | c5d.24xlarge | c5d.metal	25 Gbps	ENA
c5n.9xlarge	50 Gbps	ENA
c5n.18xlarge | c5n.metal	100 Gbps	ENA
c4.large	Moderate	Intel 82599 VF
c4.xlarge | c4.2xlarge | c4.4xlarge	High	Intel 82599 VF
c4.8xlarge	10 Gbps	Intel 82599 VF

SSD I/O Performance

If you use a Linux AMI with kernel version 4.4 or later and use all the SSD-based instance store volumes available to your instance, you get the IOPS (4,096 byte block size) performance listed in the following table (at queue depth saturation). Otherwise, you get lower IOPS performance.

Instance Size	100% Random Read IOPS	Write IOPS
c5d.large *	20,000	9,000
c5d.xlarge *	40,000	18,000
c5d.2xlarge *	80,000	37,000
c5d.4xlarge *	175,000	75,000
c5d.9xlarge	350,000	170,000
c5d.12xlarge	700,000	340,000
c5d.18xlarge	700,000	340,000
c5d.24xlarge	1,400,000	680,000
c5d.metal	1,400,000	680,000

* For these instances, you can get up to the specified performance.

As you fill the SSD-based instance store volumes 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 instance don't have any space reserved for over-provisioning. To reduce write amplification, we recommend that you 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 even if the disk is close to full capacity.

For instance store volumes that 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.

Instance Features

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

	EBS only	NVMe EBS	Instance store	Placement group
C4	Yes	No	No	Yes
C5	Yes	Yes	No	Yes
C5d	No	Yes	NVMe *	Yes
C5n	Yes	Yes	No	Yes

* The root device volume must be an Amazon EBS volume.

For more information, see the following:

• Amazon EBS and NVMe on Linux Instances

• Amazon EC2 Instance Store

• Placement Groups

Release Notes

• C5 and C5d instances feature a 3.1 GHz Intel Xeon Platinum 8000 series processor from either the first generation (Skylake-SP) or second generation (Cascade Lake).

• C4, C5, C5d, and C5n instances require 64-bit EBS-backed HVM AMIs. They have high-memory 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.

• C5, C5d, and C5n instances have the following requirements:

  • NVMe drivers must be installed

  • Elastic Network Adapter (ENA) drivers must be installed

  The following Linux AMIs meet these requirements:

  • Amazon Linux 2

  • Amazon Linux AMI 2018.03

  • Ubuntu 14.04 (with linux-aws kernel) or later

  • Red Hat Enterprise Linux 7.4 or later

  • SUSE Linux Enterprise Server 12 SP2 or later

  • CentOS 7.4.1708 or later

  • FreeBSD 11.1 or later

  • Debian GNU/Linux 9 or later

• C5, C5d, and C5n instances support a maximum of 28 attachments, including network interfaces, EBS volumes, and NVMe instance store volumes. Every instance has at least one network interface attachment.

• Launching a bare metal instance boots the underlying server, which includes verifying all hardware and firmware components. This means that it can take 20 minutes from the time the instance enters the running state until it becomes available over the network.

• To attach or detach EBS volumes or secondary network interfaces from a bare metal instance requires PCIe native hotplug support. Amazon Linux 2 and the latest versions of the Amazon Linux AMI support PCIe native hotplug, but earlier versions do not. You must enable the following Linux kernel configuration options:

  CONFIG_HOTPLUG_PCI_PCIE=y
  CONFIG_PCIEASPM=y

• Bare metal instances use a PCI-based serial device rather than an I/O port-based serial device. The upstream Linux kernel and the latest Amazon Linux AMIs support this device. Bare metal instances also provide an ACPI SPCR table to enable the system to automatically use the PCI-based serial device. The latest Windows AMIs automatically use the PCI-based serial device.

• C5, C5d, and C5n instances should have acpid installed to support clean shutdown through API requests.

• 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.