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Difficulty: Very hardConfigure Virtual Machine Scale Sets (VMSS)

You manage an Azure Virtual Machine Scale Set named `VMSS1` configured with Uniform orchestration mode. You configure an Azure Autoscale setting for `VMSS1` containing two profiles as shown in the following table:

Profile NameMinimum CapacityMaximum CapacityScale-out RuleScale-in RuleSchedule
Profile 1 (Default)2266CPU > 80% (add 1)CPU < 30% (remove 1)Always active
Profile 2 (PeakHours)661212CPU > 70% (add 2)CPU < 40% (remove 2)Monday-Friday, 08:00-18:00

On Monday at 07:55 AM, `VMSS1` has 44 running instances, and the average CPU usage is 50%50\%. The average CPU usage remains stable at 50%50\% until 08:30 AM.

At 08:30 AM, what is the total number of running instances in `VMSS1`?

  1. A
    4
  2. 6Answer
  3. C
    8
  4. D
    12

Answer

6 running instances
When Profile 2 (PeakHours) becomes active at 08:00 AM on Monday, the autoscale engine evaluates the capacity limits. Because the current instance count of 4 is less than the minimum capacity of 6 defined in Profile 2, the scale set immediately scales out to 6 instances to meet the minimum capacity requirement. Since the CPU usage remains at 50% (which is between the 40% scale-in and 70% scale-out thresholds of Profile 2), no further scaling rules are triggered by 08:30 AM, resulting in a total of 6 running instances.

Step-by-Step Solution

1
Evaluate the active autoscale profile at 07:55 AM.
Profile 1 (Default) is active with 4 instances running and CPU at 50%.
Profile 1 is always active, and since it is before 08:00 AM on Monday, the schedule for Profile 2 has not started yet.
2
Determine the active profile transition at 08:00 AM.
Profile 2 (PeakHours) becomes the active profile.
The schedule for Profile 2 is Monday through Friday, 08:00 to 18:00. At 08:00 AM on Monday, this profile takes precedence over the default profile.
3
Compare current instance count with the boundaries of the newly active profile.
The instance count is adjusted from 4 to 6.
Profile 2 defines a minimum capacity of 6. Since the current capacity is 4, Azure Autoscale immediately scales out the VMSS to meet the minimum capacity requirement.
4
Evaluate the autoscale rules for Profile 2 under the stable 50% CPU load between 08:00 AM and 08:30 AM.
No scaling actions are triggered; capacity remains at 6.
The CPU usage of 50% is within the non-scaling range (above the 40% scale-in threshold and below the 70% scale-out threshold) of Profile 2.

Key Concept

Autoscale profile capacity boundaries and scheduling
Estimated Time:3m 0s
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Topics

Configure Virtual Machine Scale Sets (VMSS)

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