Which Azure feature ensures virtual machines are spread across multiple fault domains?

Availability Sets distribute VMs across multiple fault domains (physical hardware in a datacenter) and update domains (groups of VMs that can be rebooted together during planned maintenance). This ensures that if one fault domain experiences an outage (e.g., power loss to a rack), your application remains available because other VMs are running in different fault domains. Azure Advisor provides recommendations, Azure Arc extends Azure management to on-premises and other cloud environments, and Azure Key Vault securely stores secrets, none of which directly manage VM distribution for high availability within a region.