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A
regional managed instance group (MIG)
is not balanced if the difference in the number of VMs between
two zones is 2 or more VMs. A regional MIG can fall out of balance if you
disable
proactive instance redistribution
and then delete or abandon instances to cause an uneven distribution across
zones.
If your group is not balanced and you want to re-enable proactive instance
distribution, you must first manually rebalance your group to achieve an even
distribution of instances across zones.
Manually rebalance by deleting VMs or resizing the group
You can manually rebalance your group to achieve an even distribution of
instances across zones by
deleting
VMs from zones with more instances or by
resizing
to add instances to zones with fewer VMs until the distribution is even.
When you resize a MIG that has proactive instance redistribution turned off,
the group still opportunistically converges toward balance, treating each
resize operation as an opportunity to balance the group:
When the group grows, the group always tries to add VMs to the zones with
the smallest number of VMs.
When the group shrinks, the group always removes VMs from the zones with the
largest number of VMs.
Example of manually resizing a group to achieve even redistribution
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-04-02 UTC."],[[["A regional managed instance group (MIG) is considered unbalanced when the difference in virtual machines (VMs) between two zones is two or more."],["Manually rebalancing an unbalanced MIG involves deleting VMs from zones with more instances or resizing the group to add instances to zones with fewer VMs."],["Even with proactive instance redistribution turned off, resizing a MIG will cause it to opportunistically converge toward balance by adding VMs to zones with the fewest or removing them from the zones with the most."],["Re-enabling proactive redistribution requires an initial manual rebalancing of the MIG to ensure an even distribution of instances across zones."]]],[]]
