AWS EC2 Shared , Dedicated Instance , Dedicated Host difference

AWS EC2 Shared , Dedicated Instance , Dedicated Host difference

In this article we will go-through what is AWS EC2 Shared , Dedicated Instance , Dedicated Host and difference between them .AWS has 3 types of EC2 tenancy model . Actually this will explain how your actual virtual server (EC2) hosted in real physical server.Depends on tenancy type the features and price will vary . Along with this some time limitations also will be applicable for few models of EC2 .

Where you have to choose EC2 Tenancy model

While launching EC2 instance in “Configure Instance” page you have to select the Tenancy options.

1.EC2 – Shared Tenancy model

     The above diagram shows the architecture of “Shared Tenancy Model”  and this is Default model when you launch instance.

EC2 instances are virtual machines which sit on some underlying Physical Server.Foe Ex Here H001 is physical Host .

Based on instance type some amount of CPU , RAM ,Disk allocated by Hypervisor for each instance.

I-300 is EC2 instance (Virtual Machines) of client 1 , I-400 is EC2 instance of Client 2 some other AWS account ans I-500 is EC2 instance of Client 3.

Different instance from Different AWS customers share the same physical host to run their EC2 instance is called “Shared Tenancy Model”.

Shared Tenancy – What will happen with Reboot, Stop and start Start

Its very important to understand what will happen when you reboot ,stop and start the instance , Where will sit your EC2.

Reboot – Its most closely related to OS level activity . After Rebooting the EC2 instance , it will reside on same physical host.

Stop and Start – When you stop and start the instance again the EC2 instance  it will not run on same underlying physical host .In this example the initial physical host for I-300 instance is H-2001 . After stop and start it moved to H-2001.So its very less chance to instance run on same physical host.

In H-2001 Other AWS client instances I-600 and I-700 are already running.

This is reason the when you store some data on Instance store disk , you will loose the data . Because instance store disk are attached as local to physical host . When your EC2 moved to some other physical host connectivity will be broken.

Note:Its very important to note down this characters when you are planning with “Hardware Bound” License model .Like License bounded with CPU or NIC card MAC address.

2.Dedicated Instance

Dedicated Instances are physically isolated at the host hardware level from instances that belongs to other AWS Customers.

Only your AWS account EC2 instances will run on the physical hosts . Other customer instances will not hosted on this physical host.

If you have 10 Instance on the particular region , all your 10 instance can run on this single physical host.As shown in the diagram above I-300 ,I-400 and I-500 all 3 instances belongs to single customer “Client1”

Dedicated instances may share hardware with other instances from the same AWS account that are not Dedicated instances.So shared instance type also can run on this physical host.

Dedicated Instance – What will happen with Reboot, Stop and start Start

Reboot – Its most closely related to OS level activity . After Rebooting the EC2 instance , it will reside on same physical host.

Stop and Start – When you stop and start the instance it may not run on same physical host . The instance may moved to some other physical host , but in that host also , only the instances belongs to your account can run , not from other customers.

Ex : In the above diagram it’s shows clearly  the instance I-300 (Client ) which is running on Physical host 1001 .When you stop and start the instance it’s moved to physical host 1001 . In host 1001 except I-300 no other instances are running . But other instances I-400 and I-500 still running on same physical host H-1001.

3,Dedicated Hosts

Amazon EC2 Dedicated Host is a physical server with EC2 instance capacity fully dedicated to your use .

It’s not baremetal server .Dedicated Host are the same virtualized instances that you’d get with traditional EC2 instances that use the Xen hypervisor.

The EC2 instances will always run on same physical server.In this example as per above diagram I-300 .I-400,I-500 will always run on same physical host H-1001

Dedicated Hosts provide further visibility and control by allowing you to place your instances on a specific, physical server.

Dedicated Hosts can save you money by enabling you to leverage your existing server-bound software license investments.

Allows to  use per-socket, per-core, or per-VM software licenses, including Windows Server, Microsoft SQL Server, SUSE, Linux Enterprise Server, and so on.

You can launch some limited number of instance based on EC2 instance types.

For example, if you allocate a c3.xlarge Dedicated Host, you can use a Dedicated Host with two sockets and 20 physical cores configured to support up to 8 c3.xlarge instances.Refer the link below to know how many instances can launch on dedicated host

https://aws.amazon.com/ec2/dedicated-hosts/pricing/#host-configuration

All the EC2 instances should be similar instance type . Can not mix multiple instance type. Ex you can not launch r4.large and c3.large . It should be single instance type always on entire host.

Dedicated Host- What will happen with Reboot, Stop and start Start

As stated above even after reboot ,stop and start the instance always will stay on same physical host . It will not change.

And in the point of billing You will pay the On-Demand rate for every hour the host is active in your account, regardless of the number of instances, or types of AMIs, that are running on the host.

Comparing Dedicated Hosts to Dedicated Instances

AWS Link : https://aws.amazon.com/ec2/dedicated-hosts/

Thanks!