Is a redudant cluster needed to avoid downtime when upgrading AKS cluster?

Martin Edwin Schjødt Nielsen 26 Reputation points
2021-02-20T08:26:42.707+00:00

I have been told by a consultant that there is no way to upgrade a AKS cluster without downtime, and we therefore
would need a redundant cluster to avoid downtime. To me that sounds odd. Can anyone confirm whether that is
correct or not?

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.
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  1. Supratim Sircar 186 Reputation points
    2021-02-20T08:58:59.187+00:00

    A redundant cluster is not required but you can use the max-surge setting to create new buffer nodes when some nodes are upgrading.

    For example, a cluster that has 5 node pools, each with a count of 4 nodes, has a total of 20 nodes. If each node pool has a max surge value of 50%, additional compute and IP quota of 10 nodes (2 nodes * 5 pools) is required to complete the upgrade.

    The max surge setting on a node pool is permanent. Subsequent Kubernetes upgrades or node version upgrades will use this setting. You may change the max surge value for your node pools at any time. For production node pools, Microsoft recommends a max-surge setting of 33%.

    # Set max surge for a new node pool
    az aks nodepool add -n mynodepool -g MyResourceGroup --cluster-name MyManagedCluster --max-surge 33%

    # Update max surge for an existing node pool
    az aks nodepool update -n mynodepool -g MyResourceGroup --cluster-name MyManagedCluster --max-surge 5

    ref: https://learn.microsoft.com/en-us/azure/aks/upgrade-cluster#customize-node-surge-upgrade

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