Final answer:
The feature in Azure designed to protect managed disks from a datacenter failure is Availability Zones, which offer redundancy and high availability across multiple unique physical locations within an Azure region.
Step-by-step explanation:
The feature in Azure that can be used to protect Azure managed disks from a datacenter failure is Availability Zones. Availability Zones are unique physical locations within an Azure region. Each zone is made up of one or more datacenters equipped with independent power, cooling, and networking. By architecting your solutions to use replicated VMs in zones, you can protect your applications and data from the loss of a datacenter. If one zone is compromised, the other continues working, thereby providing redundancy and high availability.
Options such as Virtual Networks, Azure Blob Storage, and Azure Active Directory are not directly designed to protect from datacenter failures in the way Availability Zones are. Virtual Networks enable network isolation, Azure Blob Storage is a service for storing large amounts of unstructured data, and Azure Active Directory is a cloud-based identity and access management service.