What is Availability Set and Availability Zone in Azure?

It`s extremely important for a cloud engineer to know about some of the important terminology used in the cloud so that you do not get confused and have a clear understanding of all the terms.

Availability is an important parameter for any Cloud Solution and we will see how we can achieve it while deploying your VM in Azure. Today in this article, we will be discussing the availability sets and availability zones in Azure.

What is Availability Set and Availability Zone in Azure? In Availability Set, VM`s copy is created and is isolated with separate physical servers, computer racks, storage units, network switches in a data center within a region so if one of the VM stops working then still we have the copy of the VM working within the same datacenter. While Availability Zone ensures that complete datacenter data is replicated to another place at a distance within the same region so that even if complete datacenter fails due to any reason then also Availability of data is ensured.

We are able to make a highly available solution using an availability set. You need to define the availability set for the VM when creating the VM and it cannot be changed later on. Availability Set applies only to Virtual Machines and no other resources in Azure.

Now let’s check the SLA provided by Availability Set and Availability Zones:


Sr No Virtual Machine SLA
1 Single VM using Premium Storage 99.90%
2 VM`s in Availability Set 99.95%
3 VM`s in Availability Zone 99.99%

Azure Region

As per Microsoft, Region is a set of data centers deployed within a latency defined perimeter and connected through a dedicated regional low-latency network. 

In Geography, there are multiple regions and some of these regions are paired so that in case of disaster and failure, failover support is provided using a secondary region.

Within a region, there are a number of zones that ensure that in case of any failure in a particular zone then data is copied to another zone that is present at a distance with in a region.

Service Level Agreement (SLA`s)

It`s an agreement for a commitment from the Microsoft meeting or exceeding the availability of Azure Services. SLA is an instrument under which user can receive compensation if Microsoft fails to meet the threshold set out in the agreement.

As per the Microsoft Documentation Virtual Machine SLA is defined as below:

If we do not achieve and maintain the Service Levels for each Service as described in this SLA, then you may be eligible for a credit towards a portion of your monthly service fees.


Difference Between Availability Set and Availability Zones

Availability Set Availability Zone
Protect from Hardware failures within data centers Protect from entire data center failure
SLA: 99.95% SLA: 99.99%


I hope this article would have help you understand the concept of Availability Set and Availability Zone. Nowadays, every cloud solution is providing highly available solution and if cloud solution provider fails to provide the availability as per the SLA then companies have to pay compensation to the client. Thus, it is extremely important to know about Availability Set and Availability Zone which ensures that Virtual Machines are available to the client as per the SLA.

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