Real meaning of having a zone-redundant VM

Question

_{Wednesday, July 31, 2019 4:23 AM}

HI,

When provisioning an Azure VM, there is an option to make it zone redundant. I can't quite understand the real meaning of it. Does it mean that a zone-redundant VM is constantly replicated to other zones in the same region so if the zone the VM is in becomes unavailable, Azure will automatically spin up the replica in another zone?

If so, I assume Azure can distinguish the difference between a zone being down (it will spin up a VM) v.s. a VM is down for patching (it will not spin up a VM in another zone)?

Thank you.

All replies (9)

_{Thursday, August 15, 2019 6:49 PM ✅Answered}

availability zone' guarantees I can pin each VM to a different zone  --> True

*** 'no infrastructure redundancy required' basically let Azure to decide which zone to create the VM, ie Azure does not guarantee all VMs with the same purpose will end up in different zones --> *yeah, it is similar to the standalone VM. ***

If this answer's your question, please mark it as answer.

**Regards, **

Msrini

_{Wednesday, July 31, 2019 4:52 AM}

Hi, 

When you deploy a VM, you can choose either Zonal or Zone redundant option. Either ways, Azure will not spin up a VM. 

In Zonal based deployment, you need to deploy VMs in different zones and manage yourselves.

In Zone redundant based deployment, you deploy VMs and Azure will decide which Zones the VM should be part of. 

Once you deployed VMs in different zones, you need to use a LB to load balance the traffic across each VMs. 

Let me know if you have any further questions. 

Regards,

Msrini 

_{Wednesday, July 31, 2019 5:40 PM}

Hi Msrini,

Thanks as always for your quick reply.

>> In Zone redundant based deployment, you deploy VMs and Azure will decide which Zones the VM should be part of. 

It does not sound like zone redundant setup replicates a copy of the VM to the other zones but only provides an option to choose which zone to place the new VM in? I don't plan to use a LB in front but I need to way to be able to bring the service back quickly in a different zone if the zone the VM is in becomes unavailable. I was hoping by have the VM zon-redundant, it keeps a copy of the VM in the other zones to achieve this goal...

thank you.

_{Wednesday, July 31, 2019 6:53 PM}

Hi, 

It is similar to that of Azure Availability Sets, where you deploy 2 copy of VMs with the same application settings and Azure will make sure your VMs are placed in different Fault domain and update domain. 

Azure Availability Zones will deploy your VMs in different Zones. So it will increase the resiliency but the concept remains the same. 

Regards, 

Msrini

_{Monday, August 5, 2019 7:04 AM}

Hi, 

Does the above response helped ? Please mark the question as answered if it helped. 

Regards, 

Msrini

_{Tuesday, August 6, 2019 10:26 AM}

Hello,

Any update on the issue?

Just checking in if you got a chance to check the previous response.

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Thanks.

_{Monday, August 12, 2019 11:42 PM}

Sorry I was out sick. 

In Zonal based deployment, you need to deploy VMs in different zones and manage yourselves.

In Zone redundant based deployment, you deploy VMs and Azure will decide which Zones the VM should be part of. 

Question #1:

During provisioning of a new VM, it has an "availability zone" field with one of the values being "availability zone". If i select it, I have to select a zone number (1,2,3). Is this the 'zone redundant deployment'? If so, since I have to choose which zone, it's not Azure deciding on the zone then? 

Question #2:

Let's say I already have a VM with zone redundant set and the zone is 1. I now provision the second VM which has the same config as the first VM. How do I tell Azure this is a 'copy' of the first VM and they should be in a different zone? 

Sorry I am just not clear on the benefit of zone redundant over zonal if both setups have two VMs in two different zones? Thanks,

_{Tuesday, August 13, 2019 8:04 AM}

Hi, 

Azure VM can only be deployed as Zonal deployments. You cannot deploy Azure VM as Zone redundant deployment.

In your case, you need to create 3 VMs in 3 different Zones, so that each VM 's storage account will also be pinned to the same Zone. Once that is done, you need to add these VMs to the back of a LB in case if it is a Web Server and load balance between each VM. 

Let me know if you have any further questions. 

Regards, 

Msrini

_{Thursday, August 15, 2019 6:29 PM}

Thanks, msrini. But when I create a new VM, i see the option for 'zone redundant' hence i am confused the difference between selecting 'no infrastructure redundancy required' vs 'availability zone'.

The only difference I can think of is

* 'availability zone' guarantees I can pin each VM to a different zone

* 'no infrastructure redundancy required' basically let Azure to decide which zone to create the VM, ie Azure does not guarantee all VMs with the same purpose will end up in different zones

Is it the only difference? Thank you.