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Difficulty: HardDesign Compute High Availability

You are designing the compute infrastructure for a high-frequency financial trading API gateway on Azure. The gateway will run on three virtual machines that must replicate state in memory. The replication protocol requires network latency between the virtual machines to be less than 1 millisecond. The business requires a minimum compute uptime SLA of 99.95% for the gateway. You need to design the compute deployment topology to meet both the availability and latency requirements. Which configuration should you recommend?

  1. Deploy the virtual machines in a single Availability Zone, associated with a single Proximity Placement Group, and distributed across multiple fault domains using a Virtual Machine Scale Set in Flexible orchestration mode.Answer
  2. B
    Deploy the virtual machines across three Availability Zones in a single region, associated with a single Proximity Placement Group.
  3. C
    Deploy the virtual machines as standalone instances within a single Availability Zone, associated with a single Proximity Placement Group, with no scale set or availability set configuration.
  4. D
    Deploy the virtual machines in an Availability Set across two Azure regions, and configure Azure Site Recovery to maintain synchronous replication.

Answer

Deploy the virtual machines in a single Availability Zone, associated with a single Proximity Placement Group, and distributed across multiple fault domains using a Virtual Machine Scale Set in Flexible orchestration mode.
The correct configuration deploys the virtual machines in a single Availability Zone, inside a Proximity Placement Group, and distributed across multiple fault domains using a Virtual Machine Scale Set in Flexible orchestration mode. This ensures that all VMs are co-located in the same datacenter to meet the sub-millisecond latency requirement, while still being separated across different physical racks to satisfy the 99.95% VM uptime SLA.

Step-by-Step Solution

1
Analyze the latency requirement (< 1 ms).
Determine that the virtual machines must be co-located within the same physical datacenter, which requires a Proximity Placement Group restricted to a single Availability Zone.
Deploying across multiple Availability Zones introduces inter-zone physical distance, causing latency to exceed the 1 millisecond threshold.
2
Analyze the uptime SLA requirement (99.95%).
Identify that the virtual machines must be distributed across different hardware racks (fault domains) within the selected Availability Zone.
An Availability Set or a Virtual Machine Scale Set in Flexible orchestration mode with a fault domain count greater than 1 provides the required 99.95% SLA for a multi-instance VM deployment.
3
Combine the placement and redundancy configurations.
Recommend deploying the VMs within a single Availability Zone, inside a Proximity Placement Group, and distributed across fault domains using a Virtual Machine Scale Set in Flexible orchestration mode.
This combination guarantees both sub-millisecond latency (via the single-zone PPG) and 99.95% availability (via fault domain isolation within that zone).

Key Concept

Balancing compute high availability SLAs with low-latency placement constraints in Azure using Proximity Placement Groups and Fault Domains.
Estimated Time:2m 30s
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Topics

Design Compute High Availability

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