AZ-900 Practice Question 44: Availability Sets
Microsoft Azure Fundamentals (AZ-900) · Test 5 · question 4 of 10
Two virtual machines run an internal web application in an Azure region that does not offer availability zones. The team wants Azure to place the VMs so that neither a single rack's power or network switch failing, nor a host reboot during planned platform maintenance, can take both down at once. What should they configure?
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Answer:
An availability set is a logical grouping of VMs that reduces the chance of correlated failures, and Microsoft notes it is especially useful in regions that don't support availability zones. It answers both halves of the stem: a fault domain is the group of VMs sharing a common power source and network switch, and VMs in a set are separated across up to three of them; an update domain is a group that can be restarted together, and during planned maintenance only one update domain is restarted at a time, with 30 minutes to recover before the next. Two or more VMs in a set also meet the 99.95% VM SLA, at no extra charge for the set itself.
Option A addresses a whole-region catastrophe rather than a rack or a host reboot, and deploying into a paired region confers no automatic protection anyway. Option B protects *stored data* across zones, but this region has no zones and disks are not the failure described. Option C is the tempting one: a load balancer distributes requests, but if both VMs happen to sit on the same rack it will faithfully route traffic to two dead machines. It has no influence over placement.
Reference: Availability sets overview