Equal AZ Distribution overview

Equal AZ Distribution ensures that your Elastigroup spreads instances evenly across selected availability zones in a region. This helps maintain high availability and consistent performance across the group.

When this orientation is enabled:

• The system checks instance distribution across all selected zones

• It keeps the number of instances equal across those zones

• If Spot capacity is unavailable in one zone, an on-demand instance launches there

• This ensures the group maintains the required capacity and distribution

Why this causes on-demand launches

Even if other zones still have available Spot capacity, the system may not use those zones. Instead, it prioritizes keeping capacity balanced across all zones.

If Spot capacity is missing in a specific zone, the system launches an on-demand instance in that zone to maintain equal distribution.

This means:

• Spot may be available in Market A

• Spot may be unavailable in Market B

• Your Elastigroup needs an instance in Market B to maintain equal distribution

• Flexera Ocean launches an on-demand instance only in Market B

Capacity rules to keep in mind

• The target capacity applies to the entire group.

• If you select X availability zones, set a target capacity that is a multiple of X to keep distribution even.

• Spot Instance Percentage or On-Demand Count settings apply per availability zone, not across the entire group.

  • Example: With two availability zones and 50% Spot allocation, the first two instances will be Spot—one in each availability zone.

Enabling Equal AZ Distribution

You can enable equal zone distribution using the Flexera console or the API.

Use the Flexera console

1. Create or edit an Elastigroup.

2. Ensure your target capacity matches (or is a multiple of) the number of availability zones you select.

3. In the Review tab, turn on Edit mode and edit the JSON.

4. Set the availabilityVsCost value to equalAzDistribution.

Use the API

To enable Equal AZ Distribution, set equalAzDistribution in the availabilityVsCost field in your Elastigroup strategy.

Example JSON:

{
  "group": {
    "strategy": {
      "risk": 100,
      "availabilityVsCost": "equalAzDistribution",
      "drainingTimeout": 60,
      "fallbackToOd": true,
      "persistence": {}
    }
  }
}

Limitations

Equal AZ Distribution isn’t supported with:

• Reserved Instances utilization

• Autoscalers such as Kubernetes, ECS, or Nomad