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Difficulty: MediumDesign Compute High Availability

A financial services company is designing the compute infrastructure for a real-time foreign exchange trading API. The application will run on 22 Azure Virtual Machines. The design must meet the following requirements:
- Provide a cumulative virtual machine uptime SLA of 99.99%99.99\%.
- Minimize network latency between the 22 virtual machines.

Which infrastructure configuration should you recommend?

  1. A
    Deploy the virtual machines in a single Availability Zone, and associate both virtual machines with a Proximity Placement Group.
  2. Deploy the virtual machines across 22 Availability Zones, and associate both virtual machines with a single Proximity Placement Group.Answer
  3. C
    Deploy the virtual machines in an Availability Set, and associate the Availability Set with a Proximity Placement Group.
  4. D
    Deploy the virtual machines as Spot VMs across 22 Availability Zones, and associate both virtual machines with a single Proximity Placement Group.

Answer

Deploy the virtual machines across 22 Availability Zones, and associate both virtual machines with a single Proximity Placement Group.
The correct option is deploying the virtual machines across two Availability Zones combined with a single Proximity Placement Group. This configuration meets the 99.99%99.99\% virtual machine uptime SLA requirement by spreading the instances across multiple zones while minimizing latency by using the Proximity Placement Group to co-locate the instances as close as possible within the regional boundaries.

Step-by-Step Solution

1
Determine the minimum SLA requirements for the virtual machines.
To achieve a 99.99%99.99\% cumulative uptime SLA, the virtual machines must be deployed across at least 22 Availability Zones in the same region.
Single-zone deployments and Availability Sets only offer up to 99.9%99.9\% and 99.9599.95\\% SLAs, respectively.
2
Evaluate the placement configuration needed to minimize inter-VM network latency.
A single Proximity Placement Group should be associated with the virtual machines.
Proximity Placement Groups tell Azure to co-locate the virtual machines physically close to each other, minimizing network latency even when they are spread across zones.
3
Select the appropriate VM lifecycle/billing model for a critical production API.
Avoid Spot VMs and choose standard on-demand or reserved instances.
Spot VMs are subject to eviction and cannot guarantee the 99.99%99.99\% SLA needed for a production trading API.

Key Concept

Azure VM SLA calculations, Availability Zones, and Proximity Placement Groups.
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Topics

Design Compute High Availability

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