AZ-104 Practice Question 7: Availability Set Versus Zones
Microsoft Azure Administrator Associate (AZ-104) · Test 1 · question 7 of 10
Three web servers run as Azure VMs in a single availability set in the West Europe region. During a recent incident, a datacenter-level power and network failure took all three VMs offline at once, even though they were spread across separate fault domains.
Management now requires the tier to stay available if one datacenter in the region fails. The VMs must remain in West Europe. What should you do?
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Answer:
An availability set spreads VMs across fault domains and update domains *within a single datacenter*, which protects against a rack-level power supply or network switch failure. It is still susceptible to shared infrastructure failures such as a datacenter-level outage, exactly what happened. Availability zones are physically separate locations within the region, each with independent power, cooling, and networking, so spreading the VMs across three zones keeps the tier serving when one datacenter is lost. That is also the difference in the SLA: 99.95% for VMs in an availability set versus 99.99% for VMs spread across zones.
Option A does not change the failure domain that matters. Three is already the maximum number of fault domains, and all of them live in the same datacenter.
Option B addresses planned maintenance, not unplanned failure. Update domains control how many VMs the platform reboots at a time during host updates; they offer no protection from a power outage.
Option C makes things worse. A proximity placement group deliberately packs VMs physically close together to minimize latency, concentrating rather than spreading the risk.
Reference: Availability sets overview