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.
By reference to this doc: Choosing the right number of fault domains for virtual machine scale set, for the regions that support zonal deployment of virtual machine scale sets and this option is selected, the default value of the fault domain count is 1 for each of the zones.
You can also consider aligning the number of scale set fault domains with the number of Managed Disks fault domains.