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Preferred Availability Zones

When you set up an Elastigroup, you choose a region, and according to the availability zones (AZs) existing in that region, you choose the availability zones that you want to be allowed for instances Spot creates.

In general, it is good practice to simply allow all the availability zones existing in that region, as shown below. This maximizes the possibilities for Spot to find spot instances that meet your exact specifications.

However, you may have specific use cases in which it is advantageous to use only certain availability zones. For example, you might want to use a reduced number or only a single AZ for the following reasons:

  • You want to reduce network costs by minimizing the number of times you change zones and transfer data from one zone to another.
  • You want to improve application performance by confining all your computing to a minimum geographic area, i.e., to only one AZ where all of your workloads run.

You can configure this in Elastigroup using the Preferred Availability Zones feature. When you define Preferred Availability Zones, Spot will always look in those availability zones first when it needs to start up a new spot instance, and it will try to launch all of your instances in those availability zones only. If no instances exist in the preferred availability zones, Spot will then consider available instances in the other availability zones you have allowed.

Step 1: Select Allowed Availability Zones​

  1. Enter the Elastigroup configuration by editing an existing Elastigroup or creating a new Elastigroup.

  2. In the Compute tab, go to Availability Zones. If you are creating a new Elastigroup, you must complete the required information in the General tab before you can enter the Compute tab.

  3. Mark all the s that you allow for the Elastigroup. For each availability zone, choose one or more subnets.

    tip

    To diversify the spot markets available to the Elastigroup, it is highly recommended to choose all the availability zones listed for the region.

Step 2: Select your Preferred Availability Zones​

  1. Go to the Predictive Rebalancing tab and scroll down to Availability Zones.
  2. The Preferred Availability Zones will now be populated with the allowed availability zones you marked in the Compute tab. Select your preferred availability zones.
  3. Complete any additional required information in the configuration and click Update.