Seeking clarification on VMSS auto scaling

Anil Kumar 480 Reputation points
2024-07-26T12:24:02.4433333+00:00

Hello,

My

I could see following information under the JSON tab for a VMSS.User's image

and under Run History tab

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Configure tab looks like this

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and finally there are logs in the Activity Log

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My questions are

  1. If Max instance count is set to 10, how observed instance count is reaching 40 ?
  2. How can i see the accurate instance count for my VMSS ? Checked metrics but couldn't find what I was looking for.
  3. When Min and Max instance count are set to same value i.e. 10, how the instance count is changing?
  4. There is no condition defined for scale in and scale out, on what basis these scale operations are happening?
  5. Does this look like flapping ?

Appreciate your insightful response.

Thank you!

Azure Virtual Machine Scale Sets
Azure Virtual Machine Scale Sets
Azure compute resources that are used to create and manage groups of heterogeneous load-balanced virtual machines.
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  1. deherman-MSFT 36,831 Reputation points Microsoft Employee
    2024-07-26T18:21:36.8833333+00:00

    @Anil Kumar

    There appears to be some flapping occurring due to your Default scale policy triggering repeatedly. You have a custom scale policy set and have minimum and maximum capacity set to the same number. When creating a new scale set it does not allow this and it is not recommended in the Best Practices page. Did you manually edit the JSON configuration to achieve this?

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    Since you want a fixed instance count of 10 it would make sense to set autoscale to manual scale. Is there a reason you want a custom scale policy instead of utilizing manual scaling? I am happy to pass this information on to our service team but want to understand the goal and use case.

    If you still have questions, please let us know in the "comments" and we would be happy to help you. Comment is the fastest way of notifying the experts.

    If the answer has been helpful, we appreciate hearing from you and would love to help others who may have the same question. Accepting answers helps increase visibility of this question for other members of the Microsoft Q&A community.

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