Exploring Dedicated Virtualization Types in AWS

Exploring Dedicated Virtualization Types in AWS
AWS offers two distinct types of dedicated virtualization to cater to different needs: at the host level and at the instance level. This post aims to outline the disparities between these two offerings.

Dedicated Host:

A Dedicated Host consists of dedicated physical hardware exclusively allocated to a single AWS account. It enables the execution of instances of various sizes within a specific instance type. The number of instances is constrained by the available cores on the host.

A Dedicated Host can be shared among multiple organizations or accounts, providing flexibility and resource optimization.

Bring Your Own License (BYOL):
Software licenses often correlate with the number of CPUs, cores, and sockets utilized. With a Dedicated Host, visibility into the core usage of each deployed instance is provided. This enables accurate tracking and validation of license compliance, making it a significant advantage of opting for a Dedicated Host.

Simplified license management can be achieved by utilizing AWS License Manager, which automatically monitors licenses when launching AMIs belonging to a license group.

Host Affinity:
When launching an instance, it is possible to target a specific Dedicated Host by specifying its host ID. This ensures that the instance maintains host affinity upon restarts, maintaining consistent performance and configuration.

Restrictions:

AMIs:

Certain operating systems (OSes) and SQL Server instances require the usage of custom AMIs, as AWS's AMIs are incompatible with Dedicated Hosts.

Host Limit:
While there is a soft limit of 2 Dedicated Hosts per family per region, it can be increased to accommodate higher requirements.

RDS:
AWS Relational Database Service (RDS) instances cannot be launched on Dedicated Hosts.

ASG:
Instances within an Auto Scaling Group (ASG) that target a Dedicated Host must be launched via a Launch Template.

Dedicated Instance:
A Dedicated Instance guarantees that it will be launched on hardware dedicated solely to the corresponding AWS account, without any instances from other accounts. However, it does not provide visibility into the underlying core utilization.

Host Affinity:
Upon restart, a Dedicated Instance may or may not be instantiated on the same physical hardware. Nevertheless, it ensures that the underlying hardware exclusively hosts instances belonging to the same AWS account.