AWS Regions, Availability Zones and Local Zones

March 17, 2020

Acronyms

AZ - Availability Zone
EC2 - Elastic Cloud Compute

Introduction

Amazon EC2 is hosted in multiple locations world-wide. These locations are composed of Regions, Availability Zones, and Local Zones. Resources aren’t replicated across Regions unless you specifically choose to do so.

Each Region is a separate geographic area.
Each Region has multiple, isolated locations known as Availability Zones.
Local Zones A Local Zone is an extension of a Region that is in a

different location from your Region. It provides you the ability to place resources, such as compute and storage, in multiple locations closer to your end users. It provides a high-bandwidth backbone to the AWS infrastructure and is ideal for latency-sensitive applications, for example machine learning.

Concepts

Each Region is completely independent. Each Availability Zone is isolated, but the Availability Zones in a Region are connected through low-latency links. The following diagram illustrates the relationship between Regions, Availability Zones, and Local Zones.

Region, AZ, Local Zone concepts

Region, AZ, Local Zone concepts. Source: docs.aws.amazon.consumers

Amazon EC2 resources are one of the following: global, tied to a Region, an Availability Zone, or a Local Zone.

Regions

Each Amazon EC2 Region is designed to be isolated from the other Amazon EC2 Regions. When you view your resources, you see only the resources that are tied to the Region that you specified.

When you launch an instance, you must select an AMI that’s in the same Region. If the AMI is in another Region, you can copy the AMI to the Region you’re using.

Note that there is a charge for data transfer between Regions

Availability Zones

Availability Zones are connected with low latency, high throughput, and

highly redundant networking.

If you distribute your instances across multiple AZs and one instance fails,

you can design your application so that an instance in another AZ can handle requests.

You can also use Elastic IP addresses to mask the failure of an instance in

one AZ by rapidly remapping the address to an instance in another AZ.

An AZ is represented by a Region code followed by a letter identifier; for

example, us-east-1a.

Note The AZ us-east-1a for your AWS account might not be the same

location as us-east-1a for another AWS account. This is because, AWS ensures that resources are distributed across the AZs by independently mapping AZs to names for each AWS account.

To coordinate AZs across accounts, you must use the AZ ID, which is a unique

and consistent identifier for an Availability Zone. For example, use1-az1 is an AZ ID for the us-east-1 Region and it has the same location in every AWS account.

Viewing AZ IDs enables you to determine the location of resources in one

account relative to the resources in another account. For example, if you share a subnet in the AZ with the AZ ID use-az2 with another account, this subnet is available to that account in the AZ whose AZ ID is also use-az2. The AZ ID for each VPC and subnet is displayed in the Amazon VPC console.

Each account might have a different number of available AZs in a Region. this

is because as AZs grow over time, AWS’ ability to expand them becomes constrained. If this happens, AWS might restrict you from launching an instance in a constrained AZ (unless you already have an instance in that AZ). Eventually, AWS might also remove the constrained AZ from the list of AZs for new accounts.

Local Zones

A Local Zone is an extension of an AWS Region in geographic proximity to your users. When you launch an instance, you can select a subnet in a Local Zone. Local Zones have their own connections to the internet and support AWS Direct Connect, so resources created in a Local Zone can serve local users with very low-latency communications.

A Local Zone is represented by a Region code followed by an identifier that indicates the location, for example, us-west-2-lax-1a.

To use a Local Zone, you must:

Enable the local Zone.
Create a subnet in the Local Zone.
Launch any of the following resources in the Local Zone subnet, so that your

applications are closer to your end users:

Amazon EC2 instances
Amazon EBS volumes
Amazon FSx file servers
Application Load Balancer
Dedicated Hosts
Local Zones are not available in every Region. You can list the Local Zones

that are available to your account. For more information, see Describing your Regions, Availability Zones, and Local Zones

Network border groups

A network border group is a unique set of Availability Zones or Local Zones from where AWS advertises IP addresses. You can allocate the following resources from a network border group: