How does Availability Zones work?

Question

How does Availability Zones work?

Derrick Nidar 20

I am new to Azure. I have a VM in Azure. If it goes down, would my VM go back up automatically through Availability Zones?

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vipullag-MSFT 26,537 Moderator

Hello Derrick Nidar

Welcome to Microsoft Q&A Platform, thanks for posting your query here.

Adding more details to previous response of Sengupta, Azure Availability Zones are a high-availability solution that protects your applications and data from datacenter-level failures.
Availability Zones are unique physical locations within an Azure region that are made up of one or more datacenters. Each Availability Zone is made up of one or more datacenters equipped with independent power, cooling, and networking. If one datacenter goes down, the other datacenters in the Availability Zone can continue to provide service.

Ref: https://learn.microsoft.com/en-us/azure/reliability/availability-zones-overview?tabs=azure-cli

For your specific question, if you have a VM in an Availability Zone, it will be automatically replicated to other datacenters within the same Availability Zone. This means that if one datacenter goes down, your VM will automatically fail over to another datacenter within the same Availability Zone, without any manual intervention.

It's important to note that not all Azure regions support Availability Zones, so you'll need to make sure that the region you're using supports them. Additionally, you'll need to make sure that your VM is configured to use Availability Zones.

Hope that helps!

Derrick Nidar 20 Reputation points

2024-04-18T13:36:15.6+00:00
Thanks S.Sengupta and vipullag.

My concern is high availability and automatic failover.

There are still some things unclear to me.

@vipullag-MSFT if my understanding is correct, if only my VM crashed and there is no issue on the datacenter, then availability zone won't automatically fail over my VM? But if the datacenter goes down, that is when automatic failover to another datacenter would work?

For the availability zone to work, do I need to have 1 VM in 1 zone, and another VM in another zone?

I checked my VM and it does say "This VM is protected from failures by availability zones". Does this mean availability zone is already working for my VM?

@S.Sengupta if I use availability sets, does it need another VM to work? If it does, does it have automatic replication as well? I am guessing availability sets would have a "primary" VM that is replicated to another VM, and when the primary VM goes down, the replicated VM will automatically start up under the same IPs, network etc?

Apologies if I have a lot of follow up questions.
Derrick Nidar 20 Reputation points

2024-04-18T13:52:52.8733333+00:00
Thanks @S.Sengupta and @vipullag-MSFT .

My main concern is actually High Availability.

I have a few more questions if you dont mind.

@vipullag-MSFT , if I undertand correctly. Availability zone will automatically replicate my VM. But it will only automatically failover if the datacenter goes down. If only my VM goes down for whatever reason, and not the whole datacenter, then the VM will not automatically failover?

Do I need to have 1 "primary" VM and a "secondary" VM for Availability zone to work?

3 @S.Sengupta , if the configuration is under availability set, does it require 1 "primary" VM and a "secondary" VM? Will the primary automatically replicate to the secondary? And it will automatically failover to the secondary if the primary VM crashed?

Thanks.
vipullag-MSFT 26,537 Reputation points Moderator

2024-04-19T04:21:06.44+00:00
Hello Derrick Nidar

To answer your questions:

If only your VM crashes and there is no issue with the datacenter, then Availability Zones won't automatically failover your VM. Availability Zones are designed to protect your applications and data from datacenter failures. If a datacenter goes down, then Availability Zones will automatically failover your VM to another datacenter within the same region.

You don't need to have one VM in one zone and another VM in another zone for Availability Zones to work. You can deploy your VMs across multiple zones within the same region to achieve high availability.

You don't need to have a primary VM and a secondary VM for Availability Zones to work. Availability Zones are designed to provide high availability for your applications and data by replicating them across multiple zones within the same region.

Simply deploying a VM in an Availability Zone does not guarantee high availability. You need to ensure that your application is designed to be highly available and that you have configured your VM to use Availability Zones correctly. To ensure that your application is highly available, you can use load balancers, auto-scaling, and other Azure services that are designed for high availability.
To configure your VM to use Availability Zones correctly, you can refer to the Azure documentation.
Hope this clarifies your queries. Please 'Accept as answer', so that it can help others in the community looking for help on similar topics.

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Derrick Nidar 20 Reputation points

2024-04-18T13:36:15.6+00:00

Thanks S.Sengupta and vipullag.

My concern is high availability and automatic failover.

There are still some things unclear to me.

@vipullag-MSFT if my understanding is correct, if only my VM crashed and there is no issue on the datacenter, then availability zone won't automatically fail over my VM? But if the datacenter goes down, that is when automatic failover to another datacenter would work?

For the availability zone to work, do I need to have 1 VM in 1 zone, and another VM in another zone?

I checked my VM and it does say "This VM is protected from failures by availability zones". Does this mean availability zone is already working for my VM?

@S.Sengupta if I use availability sets, does it need another VM to work? If it does, does it have automatic replication as well? I am guessing availability sets would have a "primary" VM that is replicated to another VM, and when the primary VM goes down, the replicated VM will automatically start up under the same IPs, network etc?

Apologies if I have a lot of follow up questions.
Derrick Nidar 20 Reputation points

2024-04-18T13:52:52.8733333+00:00

Thanks @S.Sengupta and @vipullag-MSFT .

My main concern is actually High Availability.

I have a few more questions if you dont mind.

@vipullag-MSFT , if I undertand correctly. Availability zone will automatically replicate my VM. But it will only automatically failover if the datacenter goes down. If only my VM goes down for whatever reason, and not the whole datacenter, then the VM will not automatically failover?

Do I need to have 1 "primary" VM and a "secondary" VM for Availability zone to work?

3 @S.Sengupta , if the configuration is under availability set, does it require 1 "primary" VM and a "secondary" VM? Will the primary automatically replicate to the secondary? And it will automatically failover to the secondary if the primary VM crashed?

Thanks.
vipullag-MSFT 26,537 Reputation points Moderator

2024-04-19T04:21:06.44+00:00

Hello Derrick Nidar

To answer your questions:

If only your VM crashes and there is no issue with the datacenter, then Availability Zones won't automatically failover your VM. Availability Zones are designed to protect your applications and data from datacenter failures. If a datacenter goes down, then Availability Zones will automatically failover your VM to another datacenter within the same region.

You don't need to have one VM in one zone and another VM in another zone for Availability Zones to work. You can deploy your VMs across multiple zones within the same region to achieve high availability.

You don't need to have a primary VM and a secondary VM for Availability Zones to work. Availability Zones are designed to provide high availability for your applications and data by replicating them across multiple zones within the same region.

Simply deploying a VM in an Availability Zone does not guarantee high availability. You need to ensure that your application is designed to be highly available and that you have configured your VM to use Availability Zones correctly. To ensure that your application is highly available, you can use load balancers, auto-scaling, and other Azure services that are designed for high availability.
To configure your VM to use Availability Zones correctly, you can refer to the Azure documentation.
Hope this clarifies your queries. Please 'Accept as answer', so that it can help others in the community looking for help on similar topics.

Answer 1

S.Sengupta 30,781 MVP Volunteer Moderator

Availability zones in Azure improve VM uptime, but they don't automatically restart crashed VMs. To achieve this, use availability sets: logical groupings that tell Azure to restart your VM in a healthy zone if its zone fails. For disaster recovery across regions, consider Azure Site Recovery.

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How does Availability Zones work?

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