AKS nodepool scaleset fault domains count is always 1, why? Are there any ways to change that?

Roman Aleksejuk 1 Reputation point

When deploying AKS cluster into different availability zones ("1,2,3" in our case) the vm scaleset is used for default nodepool deployment (not availability set). Everything is pretty fine there, but the problem is - while using the default nodepool scaleset, it is put into 1 fault domains only, and i did not find a way to change that (despite the fact, that the vm scaleset should be deployed into 5 fault/update domains as per documentation):


Why is it so ? How to put the nodepool into default 5 fault/update domains in addition to 3 availability zones (i mean 5 fault/update domains in each of the 3 availability zones)?

P.S. - You can always deploy AKS cluster's nodepool into availabilitySet, and have 5 update/fault domains, but then the availability zones are not available when using the availabilitySet.

Azure Kubernetes Service (AKS)
Azure Kubernetes Service (AKS)
An Azure service that provides serverless Kubernetes, an integrated continuous integration and continuous delivery experience, and enterprise-grade security and governance.
1,941 questions
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.
359 questions
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3 answers

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  1. Monalla-MSFT 12,686 Reputation points

    Hello @Roman Aleksejuk - Thanks for reaching out.

    I was able to reproduce and am looking into the source of the fault domain count not being 5. I have reached out to Engineering team and I will get back to you as soon as I have an update from them. Thank you for your patience.

  2. Michael 91 Reputation points

    AKS does not use Fault domains. You just need to ensure multiple nodes for non-zone and multiple zones for zonal.

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  3. Francesco Restelli 1 Reputation point


    Can someone elaborate more on this topic? Why should it not be important to spread accross fault domain?

    What does "AKS does not use Fault domains" mean?

    Even when adding an additional "user" scaleset pool to an existing aks cluster using the portal, the new scaleset is created with 1 fault domain!

    So is it not recommended using scalesets at this point?

    thank you br francesco

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