A company is deploying a mission-critical application on Alibaba Cloud ECS instances that require high...

A multi-zone deployment within the same region is the standard architecture for surviving the complete failure of one availability zone. Alibaba Cloud zones within a region are physically isolated for fault tolerance while maintaining high-speed internal network connectivity. Alibaba Cloud explicitly recommends deploying resources across different zones when higher disaster-recovery capability is required.

For an application tier, multiple ECS instances should be placed in separate zones and normally fronted by a multi-zone ALB or another suitable load-balancing service. Health checks ensure that traffic is no longer directed to unavailable instances, allowing surviving instances in another zone to continue serving requests. Alibaba Cloud ' s current high-availability guidance specifically describes multi-zone ECS and load-balancer deployments as the architecture for resilience against data-center or zone failures.

Option A remains vulnerable because all compute resources share the same zone failure domain. Option C retains a single compute point of failure regardless of storage performance. Option D can protect against an entire regional disaster, but it adds substantially greater networking, data synchronization, routing, and operational complexity than is necessary for the stated requirement of surviving one zone failure.

Therefore, distributing ECS instances across multiple zones within one region is the correct high-availability strategy.

Study Guide reference: Highly Available Architecture on Alibaba Cloud; Core Compute Infrastructure; multi-zone disaster recovery.