When we are moving to Amazon AWS cloud we should know some of the basic concepts like Regions, service available, security etc. In this list there is one more basic concept called Availability Zones aka AZ.

What is AWS Availability zone?

Before learning about AWS availability zones(AZ) we should know infrastructure failures. There are many times like disk failures, network failures etc below is a table containing different failures and their remedies available

Service/Device Failure Solution
Disk disk corruption/Dead Implement RAID or Backups
Network Network interrupts Network bonding/network load balancing
Power Unplanned power outages Generators

This is before 9/11 twin tower attacks where the above mention failures are taken with the mention solutions. But at the time 9/11 twin tower attacks IT people faced a strange issues some of the organizations kept their data in twin towers with above mention remedies but the issues both the building are collapsed and there is not data recovery mechanism in place. That is where people started thinking of cross site deployment of same applications in different locations.

Service/Device Failure Solution
Disk disk corruption/hardware issue Implement RAID or Backups
Network Network interrupts Network bonding/network load balancing
Power Unplanned power outages Generators
Data center location Natural calamity like cyclones Deploy same apps in different locations in High availibility mode 

From 9/11 attacks we got the concept to deploy our applications in two or more locations for service high availability. In AWS world we can achieve this by using AZ by deploying your applications in different AZ's in a given region. So in one sentence AZ is a logical division of two or more data centers in same region.

Why we require AWS availability zone?

AWS provides high availably to almost all of it’s services like two power supply for servers, two power generators for servers, two network sources etc. And completely keep a blind of our data security is not a clever decision. So better deploy your applications on VM which are located in different availability zones instead of one availability zone. A 

Advantages of AWS availability zones

Just a data security for location based disasters. We have to ensure to place our EC2 instances which are configured with HA in different AZ's in a given region.

An availability zone(AZ) is comprise of single DC or multiple DC's