Google Associate Cloud Engineer topic 1 question 33 (Page 1 of 2)

In my GCP console, I created a managed instance group for each answer.  For each answer I deleted the instance that was created as a simple test to prove or disprove each answer. 

In answer A, another instance was created after I deleted the instance 
In answer B, no other instance was created after I deleted the instance
In answer C, another instance was created after I deleted the instance
In answer D, no other instance was created after I deleted the instance

My observation is A is the correct Answer.

A - Correct - It correctly solves the problem with only a single instance at one time
B - Incorrect - Does not fit the requirement because AFTER the deletion of the instance, no other instance was created
C - Incorrect - It creates another instance after the delete HOWEVER it 2 VM's could be created even if the target is exceeded
D - Incorrect - Does not fit the requirement because AFTER the deletion of the instance, no other instance was created

thanks for confirming

Wrong! https://cloud.google.com/compute/docs/instance-groups MIGs offer the following advantages:

    High availability.
        Keeping VM instances running. If a VM in the group stops, crashes, or is deleted by an action other than an instance group management command (for example, an intentional scale in), the MIG automatically recreates that VM in accordance with the original instance's specification (same VM name, same template) so that the VM can resume its work.

I mean why don't you elaborate on Autoscaling part. If it is set to off will the MIG keep instance health?

Good point but this questions says nothing about auto-healing so we need to treat this question within context. The reason that auto-healing is not the correct way to implement this is because you can fall under your min instance number with auto-healing and not with auto-scaling. See below:
Autoscaling works independently from autohealing. If you configure autohealing for your group and an instance fails the health check, the autohealer attempts to recreate the instance. Recreating an instance can cause the number of instances in the group to fall below the autoscaling threshold (minNumReplicas) that you specify.

If you autoscale a regional MIG, an instance can be added then immediately deleted from one of the zones. This happens when the utilization in the zone triggers a scale out but the overall utilization in the regional MIG does not require the additional instance or the additional instance is required in a different zone.

Source: https://cloud.google.com/compute/docs/autoscaler

In conclusion, the answer is A.

As said in other coment, you can fix this with Autohealing, autoscaling means more machines, autohealing means re creating of VM's

A is wrong - What you are talking about is Autohealing. Autoscale will not rebuild the VM on the crash.

Read this warning message: "The minimum number of instances is equal to maximum number of instances. This means the autoscaler cannot add or remove instances from the instance group. Make sure this is the correct setting."
So when minimum is equal to maximum, it does not matter whether autoscaling is on or off. So now the question is who takes care of running the MINIMUM instances: MIG itself.

B is the answer.

B is correct. This is a trick question. Don't confuse "autoSCALING" with "autoHEALING"

A is the correct answer.

A. When autoscaling is on, we can set minimum and maximum no of instances.
B. When autoscaling is off, we cannot set minimum or maximum no of instances. Instead we set no of instances.
C. Max no of instances can't be 2 as per question.
D. Max no of instances can't be 2 as per question.

A is the correct answer