Amazon EBS volume limits for Amazon EC2 instances

The maximum number of Amazon EBS volumes that you can attach to an instance depends on the instance type and instance size. When considering how many volumes to attach to your instance, you should consider whether you need increased I/O bandwidth or increased storage capacity.

Bandwidth versus capacity

For consistent and predictable bandwidth use cases, use Amazon EBS-optimized instances with General Purpose SSD volumes or Provisioned IOPS SSD volumes. For maximum performance, match the IOPS you have provisioned for your volumes with the bandwidth available for your instance type.

For RAID configurations, you might find that arrays larger than 8 volumes have diminished performance returns due to increased I/O overhead. Test your individual application performance and tune it as required.

Volume limits for instances built on the Nitro System

The volume limits for instances built on the Nitro System depend on the instance type. Some Nitro instance types have a dedicated EBS volume limit, while most have a shared volume limit.

For more information, see Nitro-based instances.

Dedicated EBS volume limit

The following Nitro instance types have a dedicated EBS volume limit that varies depending on instance size. The limit is not shared with other device attachments. In other words, you can attach any number of EBS volumes up to the volume attachment limit, regardless of the number of attached devices, such as NVMe instance store volumes and network interfaces.

For these instance types that support dedicated volume limits, the volume limits depend on the instance size. The following table shows the limit for each instance size.

Shared EBS volume limit

All other Nitro instance types (not listed in Dedicated EBS volume limit) have a volume attachment limit that is shared between Amazon EBS volumes, network interfaces, and NVMe instance store volumes. You can attach any number of Amazon EBS volumes up to that limit, less the number of attached network interfaces and NVMe instance store volumes. Keep in mind that every instance must have at least one network interface, and that NVMe instance store volumes are automatically attached at launch.

Most Nitro instances support a maximum of 28 attachments. The following examples demonstrate how to calculate how many EBS volumes you can attach.

The following are the exceptions for instance types that have shared volume limits.

Volume limits for Xen-based instances

The volume limits for Xen-based instances, such as T2, depend on the operating system.

For more information, see Xen-based instances.

Linux instances

Attaching more than 40 volumes to a Xen-based Linux instance can cause boot failures. This number includes the root volume, plus any attached instance store volumes and Amazon EBS volumes.

If you experience boot problems on an instance with a large number of volumes, stop the instance, detach any volumes that are not essential to the boot process, start the instance, and then reattach the volumes after the instance is running.

Windows instances

The following table shows the volume limits for Xen-based Windows instances based on the driver used. That these numbers include the root volume, plus any attached instance store volumes and Amazon EBS volumes.

We recommend that you do not that attach more than 26 volumes to a Xen-based Windows instance with AWS PV or Citrix PV drivers, as it is likely to cause performance issues. To determine which PV drivers your instance is using, or to upgrade your Windows instance from Red Hat to Citrix PV drivers, see Upgrade PV drivers on EC2 Windows instances.

For more information about how device names are related to volumes, see How volumes are attached and mapped for Amazon EC2 Windows instances.