Azure availability zones confusion

Question

Azure availability zones confusion

Luis Bernardo 61

Hi, I'm Luis. I'm actually training for AZ104 certifications and I get confused by availability zones :

First question ;

Are availability zones distinct datacenters ? For example, in the Region East US, availability zones are enabled. Does that mean there are dedicated datacenters for the purpose of availability zones apart from "primary" datacenters ?

Second question :

If I select I select availability zones 1, does that mean, if a create a VM, that it will be automatically replicated to another datacenter ?

Thank you... this is driving me crazy!

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Answer 1

Andreas Baumgarten 123.7K MVP Volunteer Moderator

Hi @Luis Bernardo .

Regarding 1: An Availabilty Zone in Azure "contains" one or multiple Azure datacenter(s).

Regarding 2: What is your definition of "primary datacenter"? If you create a VM in one Availability Zone, for instance in Zone 1, only one VM will be created -> in Zone 1. Period.

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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)

Regards
Andreas Baumgarten

Answer 2

Andreas Baumgarten 123.7K MVP Volunteer Moderator

Hi @LuisBernardo-4843 ,

regarding 1st question: Yes.
regarding 2nd question: No, only one VM in zone 1 will be created. There will be no additional VMs created automatically in other zones. You have to select more than one zone to create multiple VMs in different zones.

Good explanation that might be helpful: https://www.youtube.com/watch?v=4Au2QW6lsYI

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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)

Regards
Andreas Baumgarten

Answer 3

Thank you Andreas !

So, if I create a VM with an availability zone, it means I'll have one VM on a "primary" datacenter and another in an AZ ? Is there replication ? I get two VMs with the same data ?

Also you say : "You have to select more than one zone to create multiple VMs in different zones." => When I create a VM I get to choose between 1,2 or 3 ? Does it mean AZ1, AZ2, AZ3 or the number of AZ ? In the video we can see checkboxes, but in the portal I just can choose between 1 or 2 or 3...

(pardon me for my english)

Is the image correct ?

Answer 4

srbhatta-MSFT 8,586 Microsoft Employee

Hello @Luis Bernardo ,
Welcome to Microsoft QnA.
To build on top of Andreas, and to answer your query, as per your diagram zone 1 will represent AZ1, zone 2 represents AZ2 and zone 3 will represent AZ3. To take advantage of the benefits of availability zones, you will need to deploy your resources across multiple availability zones within a region. This can be done manually, by creating resources in different availability zones, or automatically, using Azure's built-in high availability and disaster recovery features.

If you want to replicate your VMs to another availability zone within the same region, you can use Azure Site Recovery. This service allows you to replicate your VMs to a secondary location, where they can be automatically failed over in the event of an outage or disaster. To set up Site Recovery, you will need to create a recovery plan that specifies the source and target VMs, as well as the recovery options and settings.

Hope that clears your query!

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Luis Bernardo 61 Reputation points

2022-12-30T18:10:50.917+00:00
@Andreas Baumgarten

A free sub. It's probably the reason.

@srbhatta-MSFT

Thx for your answer but I still get confused...

Is my diagram correct? Availability zones are dedicated data centers for availability?

If I create one VM and I choose availability zone 1. What happens? :

-It creates a VM on a primary data center AND the same VMavailability zone 1 (so 2 VMs)?

(If not, I don't get the point of choosing an availability zone and how this gets me a 99.9% sla)

Or

It only creates a VM on availability zone 1.

Thank you...
srbhatta-MSFT 8,586 Reputation points Microsoft Employee

2023-01-02T06:14:36.94+00:00

It only creates a VM on availability zone 1
srbhatta-MSFT 8,586 Reputation points Microsoft Employee

2023-01-03T08:38:56.21+00:00
@Luis Bernardo ,

Yes, your diagram is correct. Availability Zones are basically separate datacenters in a region that are connected by a high-performance network with a round-trip latency of less than 2ms. Each zone is composed of one or more datacenters equipped with independent power, cooling, and networking infrastructure.
The physical separation of availability zones within a region limits the impact to applications and data from zone failures, such as large-scale flooding, major storms and superstorms, and other events that could disrupt site access, safe passage, extended utilities uptime, and the availability of resources.
Availability zones are designed so that if one zone is affected, regional services, capacity, and high availability are supported by the remaining two zones. Each region might not support availability zones.

Now, to answer your second question. If there is no zone/infrastructure-redundancy, and you deploy a single VM, the uptime SLA for the VM would be 99.9%. I am not sure in which context are you using primary datacenter, but when you are deploying a VM in zone 1, then only one VM gets deployed (in zone 1), you will have to manually deploy another VM in zone 2 or 3 to achieve HA.
You can also refer to this official Microsoft documentation to understand more : Building solutions for high availability
Please let me know if this clarifies your doubt? If not, I can help explain more.
Luis Bernardo 61 Reputation points

2023-01-03T10:05:07.62+00:00

I'v made a mistake. I wanted to say 99.99% SLA.

So if my diagram is correct, I'm lost..

If a choose availability zone 1, my vm will only be in a data center of this av-zone 1. What's the point of doing that?

There's no redundancy.

Why is this even an option
srbhatta-MSFT 8,586 Reputation points Microsoft Employee

2023-01-06T05:09:56.073+00:00

Hello @Luis Bernardo , apologies for the confusion.
Could you please go through the below portion (As shown in image) of this document -> building-solutions-for-high-availability .

If you still have confusion, I would recommend you to open a support case with Azure where one of our support team members will get on a call with you to explain further.

Answer 5

Andreas Baumgarten 123.7K MVP Volunteer Moderator

Hi @Luis Bernardo ,

here the "Create VM" wizard of the portal looks different. I am able to select the zones via checkbox.

What type of subscription are you using?

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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)

Regards
Andreas Baumgarten

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Azure availability zones confusion

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