You have an on-premises network that contains several servers. You plan to migrate all the servers to Azure. You need to recommend a solution to…

Fault tolerance is the principle of designing a system to continue operating without interruption even if some of its components fail. The scenario requires a solution to ensure server availability if a single Azure data center goes offline. This is a component failure. Implementing a fault-tolerant architecture, for example, by deploying virtual machines across multiple Availability Zones (which are physically separate data centers within a region), directly addresses this requirement, ensuring the service remains available.

B. elasticity: This refers to the ability to automatically scale computing resources up or down based on demand, not to withstand a data center failure.

C. scalability: This is the ability to increase or decrease resources to handle workload changes, which is related to performance and capacity, not resilience to outages.

D. low latency: This refers to minimizing network delay to improve responsiveness and is a performance metric, not a strategy for availability during a data center failure.

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1. Microsoft Learn, AZ-900: Describe concepts of reliability and resiliency. In the "Describe high availability and disaster recovery on Azure" unit, under the section "What is high availability?", it states: "Fault tolerance is the ability of a system to remain operational in the event of a failure of some of its components." This directly defines the correct term for the scenario.

2. Microsoft Azure Documentation, "Regions and Availability Zones in Azure." Under the "Availability Zones" section, the documentation explicitly states: "Availability Zones is a high-availability offering that protects your applications and data from datacenter failures." This confirms that using features designed for fault tolerance protects against the exact event described in the question.

3. Microsoft Azure Well-Architected Framework, "Reliability design principles." The principle "Design for failure" states: "A reliable workload must be resilient and available. Resiliency is the ability of the system to recover from failures and continue to function. Availability is the measure of whether your system is running and accessible." The scenario is a direct application of designing for failure, which is achieved through fault tolerance.

4. Microsoft Learn, AZ-900: Describe the benefits and considerations of using cloud services. In the "Describe cloud computing" unit, under the section "What is cloud computing?", elasticity and scalability are defined in terms of adjusting resources to meet demand, distinguishing them from fault tolerance, which is about handling failures.