# Amazon EC2 Dedicated Hosts
An Amazon EC2 Dedicated Host is a physical server that is fully dedicated for your use. You can optionally choose to share the instance capacity with other AWS accounts. For more information, see [Cross-account Amazon EC2 Dedicated Host sharing](dh-sharing.md).
Dedicated Hosts provide visibility and control over instance placement and they support host affinity. This means that you can launch and run instances on specific hosts, and you can ensure that instances run only on specific hosts. For more information, see [Amazon EC2 Dedicated Host auto-placement and host affinity](dedicated-hosts-understanding.md).
Dedicated Hosts provide comprehensive Bring Your Own License (BYOL) support. They allow you to use your existing per-socket, per-core, or per-VM software licenses, including Windows Server, SQL Server, SUSE Linux Enterprise Server, Red Hat Enterprise Linux, or other software licenses that are bound to VMs, sockets, or physical cores, subject to your license terms.
If you require your instances to run on dedicated hardware, but you do not need visibility or control over instance placement, and you do not need to use per-socket or per-core software licenses, you can consider using Dedicated Instances instead. Dedicated Instances and Dedicated Hosts can both be used to launch Amazon EC2 instances onto dedicated physical servers. There are no performance, security, or physical differences between Dedicated Instances and instances on Dedicated Hosts. However, there are some key differences between them. The following table highlights some of the key differences between Dedicated Instances and Dedicated Hosts:
| | Dedicated Host | Dedicated Instance |
| --- | --- | --- |
| Dedicated physical server | Physical server with instance capacity fully dedicated to your use. | Physical server that's dedicated to a single customer account. |
| Instance capacity sharing | Can share instance capacity with other accounts. | Not supported |
| Billing | Per-host billing | Per-instance billing |
| Visibility of sockets, cores, and host ID | Provides visibility of the number of sockets and physical cores | No visibility |
| Host and instance affinity | Allows you to consistently deploy your instances to the same physical server over time | Not supported |
| Targeted instance placement | Provides additional visibility and control over how instances are placed on a physical server | Not supported |
| Automatic instance recovery | Supported. For more information, see [Amazon EC2 Dedicated Host recovery](dedicated-hosts-recovery.md). | Supported |
| Bring Your Own License (BYOL) | Supported | Partial support \$1 |
| Capacity Reservations | Not supported | Supported |
\$1 Microsoft SQL Server with License Mobility through Software Assurance, and Windows Virtual Desktop Access (VDA) licenses can be used with Dedicated Instance.
For more information about Dedicated Instances, see [Amazon EC2 Dedicated Instances](dedicated-instance.md).
## Dedicated Hosts restrictions
Before you allocate Dedicated Hosts, take note of the following limitations and restrictions:
+ To run RHEL and SUSE Linux on Dedicated Hosts, you must bring your own AMIs. You can't use the RHEL and SUSE Linux AMIs that are offered by AWS or that are available on AWS Marketplace with Dedicated Hosts. For more information about how to create your own AMI, see [Bring your own software licenses to Amazon EC2 Dedicated Hosts](dedicated-hosts-BYOL.md).
This restriction does not apply to hosts allocated for high memory instances (`u-6tb1.metal`, `u-9tb1.metal`, `u-12tb1.metal`, `u-18tb1.metal`, and `u-24tb1.metal`). RHEL and SUSE Linux AMIs that are offered by AWS or that are available on AWS Marketplace can be used with these hosts.
+ There is a limit on the number of running Dedicated Hosts per instance family per AWS account per Region. Quotas apply to running instances only. If your instance is pending, stopping, or stopped, it does not count towards your quota. To view the quotas for your account, or to request a quota increase, use the [ Service Quotas console](https://console.aws.amazon.com/servicequotas/home/services/ec2/quotas).
+ Auto Scaling groups are supported when using a launch template that specifies a host resource group. For more information, see [Create a launch template using advanced settings](https://docs.aws.amazon.com/autoscaling/ec2/userguide/advanced-settings-for-your-launch-template.html) in the *Amazon EC2 Auto Scaling User Guide*.
+ Amazon RDS instances are not supported.
+ The AWS Free Usage tier is not available for Dedicated Hosts.
+ Instance placement control refers to managing instance launches onto Dedicated Hosts. You can't launch Dedicated Hosts into placement groups.
+ If you allocate a host for a virtualized instance type, you can't modify the instance type to a `.metal` instance type after the host is allocated. For example, if you allocate a host for the `m5.large` instance type, you can't modify the instance type to `m5.metal`.
Similarly, if you allocate a host for a `.metal` instance type, you can't modify the instance type to a virtualized instance type after the host is allocated. For example, if you allocate a host for the `m5.metal` instance type, you can't modify the instance type to `m5.large`.
**Topics**
+ [Dedicated Hosts restrictions](#dedicated-hosts-limitations)
+ [Pricing and billing](dedicated-hosts-billing.md)
+ [Instance capacity configurations](dedicated-hosts-limits.md)
+ [Burstable instances on Dedicated Hosts](burstable-t3.md)
+ [Bring your own licenses](dedicated-hosts-BYOL.md)
+ [Auto-placement and affinity](dedicated-hosts-understanding.md)
+ [Allocate a Dedicated Host](dedicated-hosts-allocating.md)
+ [Launch instances on a Dedicated Host](launching-dedicated-hosts-instances.md)
+ [Launch instances into a host resource group](launching-hrg-instances.md)
+ [Modify Dedicated Host auto-placement](modify-host-auto-placement.md)
+ [Modify supported instance types](modify-host-support.md)
+ [Modify tenancy and affinity for an instance](moving-instances-dedicated-hosts.md)
+ [Release Dedicated Host](dedicated-hosts-releasing.md)
+ [Migrate to Nitro-based Amazon EC2 Dedicated Hosts](dh-migrate.md)
+ [Purchase a Dedicated Host Reservation](#purchasing-dedicated-host-reservations)
+ [Cross-account sharing](dh-sharing.md)
+ [Dedicated Hosts on Outposts](dh-outposts.md)
+ [Host recovery](dedicated-hosts-recovery.md)
+ [Host maintenance](dedicated-hosts-maintenance.md)
+ [Monitor Dedicated Hosts](dedicated-hosts-monitoring.md)
+ [Track configuration changes](dedicated-hosts-aws-config.md)
## Purchase Dedicated Host Reservations for Dedicated Host billing discounts
Dedicated Host Reservations provide you with a discount of up to 70 percent compared to On-Demand Dedicated Host pricing. You must have active Dedicated Hosts allocated in your account before you can purchase Dedicated Host Reservations. For more information, see [Dedicated Host Reservations](dedicated-hosts-billing.md#dedicated-host-reservations).
------
#### [ Console ]
**To purchase reservations**
1. Open the Amazon EC2 console at [https://console.aws.amazon.com/ec2/](https://console.aws.amazon.com/ec2/).
1. Choose **Dedicated Hosts**, **Dedicated Host Reservations**, **Purchase Dedicated Host Reservation**.
1. On the **Find offerings** screen, do the following:
1. For **Instance family**, select the instance family of the Dedicated Host for which to purchase the Dedicated Host Reservation.
1. For **Payment option**, select and configure your preferred payment option.
1. Choose **Next**.
1. Select the Dedicated Hosts with which to associate the Dedicated Host Reservation, and then choose **Next**.
1. (*Optional*) Assign tags to the Dedicated Host Reservation.
1. Review your order and choose **Purchase**.
------
#### [ AWS CLI ]
**To purchase reservations**
1. Use the [describe-host-reservation-offerings](https://docs.aws.amazon.com/cli/latest/reference/ec2/describe-host-reservation-offerings.html) command to list the available offerings that match your needs. The following example lists the offerings that support instances in the `m4` instance family and have a one-year term.
The term is specified in seconds. A one-year term includes 31,536,000 seconds, and a three-year term includes 94,608,000 seconds.
```
aws ec2 describe-host-reservation-offerings \
--filter Name=instance-family,Values=m4 \
--max-duration 31536000
```
The command returns a list of offerings that match your criteria. Note the ID of the offering to purchase.
1. Use the [purchase-host-reservation](https://docs.aws.amazon.com/cli/latest/reference/ec2/purchase-host-reservation.html) command to purchase the offering and provide the `offeringId` noted in the previous step. The following example purchases the specified reservation and associates it with a specific Dedicated Host that is already allocated in the AWS account, and it applies a tag with a key of `purpose` and a value of `production`.
```
aws ec2 purchase-host-reservation \
--offering-id hro-03f707bf363b6b324 \
--host-id-set h-013abcd2a00cbd123 \
--tag-specifications 'ResourceType=host-reservation,Tags={Key=purpose,Value=production}'
```
------
#### [ PowerShell ]
**To purchase reservations**
1. Use the [Get-EC2HostReservationOffering](https://docs.aws.amazon.com/powershell/latest/reference/items/Get-EC2HostReservationOffering.html) cmdlet to list the available offerings that match your needs. The following examples list the offerings that support instances in the `m5` instance family and have a one-year term.
The term is specified in seconds. A one-year term includes 31,536,000 seconds, and a three-year term includes 94,608,000 seconds.
```
$filter = @{Name="instance-family"; Values="m5"}
Get-EC2HostReservationOffering `
-Filter $filter `
-MaxDuration 31536000
```
The command returns a list of offerings that match your criteria. Note the ID of the offering to purchase.
1. Use the [New-EC2HostReservation](https://docs.aws.amazon.com/powershell/latest/reference/items/New-EC2HostReservation.html) cmdlet to purchase the offering and provide the offering ID noted in the previous step. The following example purchases the specified reservation and associates it with a specific Dedicated Host that is already allocated in the AWS account.
```
New-EC2HostReservation `
-OfferingId hro-03f707bf363b6b324 `
-HostIdSet h-013abcd2a00cbd123
```
------