Hotspot Question You have an Azure subscription. You plan to use Azure Resource Manager templates to deploy 50 Azure virtual machines that will be part of the same availability set. You need to ensure

Question

Exhibit

Answer Area

• platformFaultDomainCountmax value
  max value020
• platformUpdateDomainCountmax value
  max value020

Explanation

This question tests your knowledge of Azure Availability Sets and how to configure fault domains and update domains in an ARM template to maximize VM availability during hardware failures or planned maintenance.

Approach. For an availability set with 50 VMs, you should set 'platformFaultDomainCount' to 3 and 'platformUpdateDomainCount' to 20. Azure supports a maximum of 3 fault domains (which protect against unplanned hardware failures by distributing VMs across separate physical racks with independent power and networking), and up to 20 update domains (which protect against planned maintenance by ensuring not all VMs are rebooted simultaneously). Setting fault domains to 3 ensures VMs are spread across 3 isolated physical racks, minimizing the impact of hardware failures. Setting update domains to 20 (the maximum allowed) means during servicing/updates, only a small fraction of VMs (50/20 = ~2-3 VMs) will be unavailable at any one time, keeping as many VMs as possible running.

Concept tested. Azure Availability Sets configuration in ARM templates - specifically the maximum values for platformFaultDomainCount (max 3) and platformUpdateDomainCount (max 20), and how these values distribute VMs to maximize availability during both unplanned hardware failures and planned maintenance windows.

Reference. https://docs.microsoft.com/en-us/azure/virtual-machines/availability-set-overview

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