EC2 Dedicated Host vs Dedicated Instances

Each instance launched into a VPC has a tenancy attribute.
- default
  - is the default option
  - instances run on shared hardware.
  - all instances launched would be shared, unless you explicitly specify a different tenancy during the instance launch.
- dedicated
  - instance runs on single-tenant hardware.
  - all instances launched would be dedicated
  - can’t be changed to default after creation
- host
  - instance runs on a Dedicated Host, which is an isolated server with configurations that you can control.

Tenancy conversion rules (instance must be in stopped state):
- default tenancy can be changed to dedicated or host.
- dedicated tenancy can be changed to default or host.
- host tenancy can be changed to dedicated or default (except for T3 instances, which cannot change from host to dedicated or default).
- Changes take effect the next time the instance starts.
- Tenancy conversions are managed through AWS License Manager tenancy conversion with billing code restrictions (e.g., Windows BYOL not permitted on shared tenancy, license-included SQL Server/SUSE not permitted on Dedicated Hosts).

VPC tenancy of dedicated can’t be changed to default after creation.
Dedicated Hosts and Dedicated Instances can both be used to launch EC2 instances onto physical servers that are dedicated for your use.
There are no performance, security, or physical differences between Dedicated Instances and instances on Dedicated Hosts.

Dedicated Host vs Dedicated Instances

Feature	Dedicated Host	Dedicated Instance
Dedicated physical server	Physical server with instance capacity fully dedicated to your use	Physical server dedicated to a single customer account
Instance capacity sharing	Can share capacity with other accounts via AWS RAM	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 consistent deployment to the same physical server	Not supported
Targeted instance placement	Provides control over how instances are placed on a physical server	Not supported
Automatic instance recovery	Supported	Supported
Bring Your Own License (BYOL)	Comprehensive support	Partial support (SQL Server with License Mobility, Windows VDA only)
Capacity Reservations	Not supported	Supported

Dedicated Hosts

EC2 Dedicated Host is a physical server with EC2 instance capacity fully dedicated to your use.
provides Affinity that allows you to specify which Dedicated Host an instance will run on after it has been stopped and restarted.
Dedicated Hosts provide visibility and the option to control how you place your instances on a specific, physical server. This enables you to deploy instances using configurations that help address corporate compliance and regulatory requirements.

Dedicated Hosts allow using existing per-socket, per-core, or per-VM software licenses, including Windows Server, Microsoft SQL Server, SUSE Linux Enterprise Server, Red Hat Enterprise Linux, or other software licenses that are bound to VMs, sockets, or physical cores.
Dedicated Host is also integrated with AWS License Manager, a service that helps you manage your software licenses, including Microsoft Windows Server and Microsoft SQL Server licenses.
Dedicated Hosts support Host Resource Groups through AWS License Manager, allowing you to manage a collection of Dedicated Hosts as a single entity with automated host allocation and license tracking.

Dedicated Hosts can be shared across AWS accounts using AWS Resource Access Manager (RAM), allowing other accounts to launch instances on your Dedicated Hosts.
Dedicated Hosts support both single instance type and multiple instance type configurations within the same instance family.
RDS instances are not supported.
Dedicated Hosts cannot be launched in placement groups.
SQL Server, SUSE, and RHEL AMIs provided by Amazon EC2 cannot be used with Dedicated Hosts (BYOL only for these).

AWS recommends migrating from Xen-based Dedicated Hosts to Nitro-based Dedicated Hosts for improved price performance.

Dedicated Host Maintenance

Live Migration-based Host Maintenance (October 2024) – AWS now supports live migration for Dedicated Hosts during maintenance events. When a host requires maintenance, AWS allocates a replacement Dedicated Host and moves instances to the new host automatically within 24 hours, without stopping and restarting them.
Host Recovery – Automatically detects hardware issues and migrates instances to a replacement host, minimizing disruption.

If host maintenance is disabled, you receive notification to manually migrate instances within 28 days. After 28 days, instances are terminated and the host is released.
EC2 Mac Dedicated Hosts (August 2025) – Now support Host Recovery and Reboot-based Host Maintenance for Mac instances.

Dedicated Host Auto-Placement

When auto-placement is enabled, instances launched with host tenancy (without a specific host ID) are automatically placed on any available Dedicated Host with matching instance type.

When auto-placement is disabled, you must provide a specific host ID for instance launch.
Auto-placement works with Host Resource Groups in License Manager for automated host management and allocation.

Dedicated Instances

Dedicated Instances are EC2 instances that run in a VPC on hardware that’s dedicated to a single customer.

Dedicated Instances are physically isolated at the host hardware level from the instances that aren’t Dedicated Instances and from instances that belong to other AWS accounts.
Dedicated Instances may share hardware with other instances from the same AWS account that are not Dedicated Instances.
Dedicated Instances provide no visibility or control over instance placement and do not support host affinity.

Dedicated Instances provide limited support for Bring Your Own License (BYOL).
Dedicated Instances can be launched using:
- Create the VPC with the instance tenancy set to dedicated – all instances launched into this VPC are Dedicated Instances.
- Create the VPC with the instance tenancy set to default, and specify dedicated tenancy for any instances that should be Dedicated Instances when launched.
Dedicated Instances support:
- Reserved Instances and Capacity Reservations
- Auto Scaling
- Automatic instance recovery
- Spot Instances (Dedicated Spot Instances)
- Burstable performance instances (T3)
EBS volumes attached to Dedicated Instances do NOT run on single-tenant hardware.

AWS Certification Exam Practice Questions

Questions are collected from Internet and the answers are marked as per my knowledge and understanding (which might differ with yours).

AWS services are updated everyday and both the answers and questions might be outdated soon, so research accordingly.

AWS exam questions are not updated to keep up the pace with AWS updates, so even if the underlying feature has changed the question might not be updated

Open to further feedback, discussion and correction.

A company wants its instances to run on single-tenant hardware with dedicated hardware for compliance reasons. Which value should they have to set the instance’s tenancy attribute to?
1. Dedicated
2. Isolated
3. Default
4. Reserved
A company is performing migration from on-premises to AWS cloud. They have a compliance requirement for application hosting on physical servers to be able to use existing server-bound software licenses. Which AWS EC2 purchase type would help fulfill the requirement?
1. Spot instances
2. Reserved instances
3. On-demand instances
4. Dedicated Hosts
A company runs licensed software that requires visibility into the physical cores and sockets of the underlying server. Which EC2 tenancy option provides this visibility?
1. Default tenancy
2. Dedicated Instances
3. Dedicated Hosts
4. Placement Groups

A company uses EC2 Dedicated Hosts and wants to minimize downtime during host maintenance events. Which feature should they enable? (Select TWO)
1. Live migration-based host maintenance
2. Enhanced networking
3. Host Recovery
4. Elastic Fabric Adapter
5. Placement Groups
A company wants to share Dedicated Host capacity with other AWS accounts in their organization. Which AWS service enables this?
1. AWS Organizations
2. AWS Resource Access Manager (RAM)
3. AWS License Manager
4. AWS Service Catalog
Which of the following statements about Dedicated Instances is CORRECT? (Select TWO)
1. EBS volumes attached to Dedicated Instances do NOT run on single-tenant hardware
2. Dedicated Instances provide visibility into the number of physical cores
3. Dedicated Instances may share hardware with other non-dedicated instances from the same account
4. Dedicated Instances support host affinity
5. Dedicated Instances cannot use Spot pricing