Availability zones for Virtual Machines

Question

I'm a bit confused after reading a LOT of Microsoft documentation on VMs and Availability Zones. If I create a VM in East US 2 and place it in an availability zone, and that zone goes down, is my VM inaccessible? I can't seem to get a clear answer on this.

Thanks ahead of time

Answer 1

Hi @richardwolford-7948 ,

based on the scenario you described above the the "single" VM will be unavailable if the zone goes down.
Availability zones don't work with single VMs. But if an IT service is running on more than one VM the Availability Zones could make sense.

For example: AD Domain Controllers
If you create 2 Domain Controller VMs it makes sense to create the 2 VMs in different Availability Zones (e.g. DC1 in Zone 1 and DC2 in Zone 2).
if both zones are up -> Everything is working fine, bot VMs are up and running and doing their job -> AD service is up
Zone 1 goes down -> DC1 is unavailable, DC2 is up and running and is doing the job -> AD service is up
Zone 2 goes down -> DC2 is unavailable, DC1 is up and running and is doing the job -> AD service is up
Zone 1 and Zone 2 goes down -> DC1 is unavailable, DC2 is unavailable -> AD service is down

Another example could be web server (with zone redundant Load Balancer) ... or SQL Server clusters.

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Regards
Andreas Baumgarten