Configure zone redundancy for Azure Functions

1. To create a function app in a zone-redundant plan, you must have an existing zone-redundant storage account. If you don't already have a zone-redundant storage account, create one before you proceed.

2. In the Azure portal, go to the Create Function App page. For more information about creating a function app in the portal, see Create a function app.

3. Select Flex Consumption and then select the Select button.

4. On the Create Function App (Flex Consumption) page, on the Basics tab, enter the settings for your function app. Pay special attention to the settings in the following table (also highlighted in the following screenshot), which have specific requirements for zone redundancy.

   Setting	Suggested value	Notes for zone redundancy
   Region	Your preferred supported region	The region in which your Flex Consumption plan is created. For a list of regions that support zone redundancy for Azure Functions Premium plans, see Reliability in Azure Functions - Resilience to availability zone failures - Requirements.
   Zone redundancy	Enabled	This setting specifies whether your app is zone redundant. You can only select Enabled when you've chosen a region that supports zone redundancy.

   

5. On the Storage tab, select the zone-redundant storage account for your function app. Pay special attention to the setting in the following table, which has specific requirements for zone redundancy.

   Setting	Suggested value	Notes for zone redundancy
   Storage account	A zone-redundant storage account	As described in the reliability guide for Azure Functions, we strongly recommend using a zone-redundant storage account for your zone-redundant function app.

6. For the rest of the function app creation process, create your function app as normal. There are no settings in the rest of the creation process that affect zone redundancy.

1. When creating the storage account for the function app, choose a zone redundant SKU, like Standard_ZRS. For example:

   az storage account create \
     --name <STORAGE_NAME> \
     --location <REGION> \
     --resource-group <RESOURCE_GROUP> \
     --sku Standard_ZRS \
     --allow-blob-public-access false
   

2. When creating the Flex Consumption plan and app, add the --zone-redundant true parameter:

   az functionapp create \
     --resource-group <RESOURCE_GROUP> \
     --name <APP_NAME> \
     --storage-account <STORAGE_NAME> \
     --flexconsumption-location <REGION> \
     --runtime <RUNTIME> \
     --runtime-version <RUNTIME_VERSION> \
     --zone-redundant true 
   

You can use a Bicep file to deploy to a zone-redundant Flex Consumption plan. To learn how to deploy function apps to a Flex Consumption, see Automate resource deployment in Azure Functions.

The only properties to be aware of while creating a zone-redundant hosting plan are the zoneRedundant property. The zoneRedundant property must be set to true.

Following is a Bicep template snippet for a zone-redundant, Flex Consumption plan. It shows the zoneRedundant field specification.

resource flexFuncPlan 'Microsoft.Web/serverfarms@2024-04-01' = {
  name: <YOUR_PLAN_NAME>
  location: <YOUR_REGION_NAME>
  kind: 'functionapp'
  sku: {
    tier: 'FlexConsumption'
    name: 'FC1'
  }
  properties: {
    reserved: true
    zoneRedundant: true
  }
}

To learn more about these templates, see Automate resource deployment in Azure Functions.

You can use an ARM template to deploy to a zone-redundant Flex Consumption plan. To learn how to deploy function apps to a Flex Consumption plan, see Automate resource deployment in Azure Functions.

The only properties to be aware of while creating a zone-redundant hosting plan are the zoneRedundant property. The zoneRedundant property must be set to true.

Following is an ARM template snippet for a zone-redundant, Flex Consumption plan. It shows the zoneRedundant field specification.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Web/serverfarms",
      "apiVersion": "2024-04-01",
      "name": "<YOUR_PLAN_NAME>",
      "location": "<YOUR_REGION_NAME>",
      "kind": "functionapp",
      "sku": {
        "tier": "FlexConsumption",
        "name": "FC1"
      },
      "properties": {
        "reserved": true,
        "zoneRedundant": true
      }
    }
  ]
}

To learn more about these templates, see Automate resource deployment in Azure Functions.

1. In the Azure portal, go to the Create Function App page. For more information about creating a function app in the portal, see Create a function app.

2. Select Functions Premium and then select the Select button.

3. On the Create Function App (Functions Premium) page, on the Basics tab, enter the settings for your function app. Pay special attention to the settings in the following table (also highlighted in the following screenshot), which have specific requirements for zone redundancy.

   Setting	Suggested value	Notes for zone redundancy
   Region	Your preferred supported region	The region in which your Elastic Premium plan is created. You must pick a region that supports availability zones. For a list of regions that support zone redundancy for Azure Functions Premium plans, see Reliability in Azure Functions - Resilience to availability zone failures - Requirements.
   Pricing plan	One of the Elastic Premium plans. For more information, see Available instance SKUs.	This article describes how to create a zone redundant app in a Premium plan. Zone redundancy isn't currently available in Consumption plans. For information on zone redundancy on App Service plans, see Configure availability zones for App Service.
   Zone redundancy	Enabled	This setting specifies whether your app is zone redundant. You won't be able to select Enabled unless you have chosen a region that supports zone redundancy, as described previously.

   

4. On the Storage tab, enter the settings for your function app storage account. Pay special attention to the setting in the following table, which has specific requirements for zone redundancy.

   Setting	Suggested value	Notes for zone redundancy
   Storage account	A zone-redundant storage account	As described in the reliability guide for Azure Functions, we strongly recommend using a zone-redundant storage account for your zone-redundant function app.

5. For the rest of the function app creation process, create your function app as normal. There are no settings in the rest of the creation process that affect zone redundancy.

1. When creating the storage account for the function app, choose a zone redundant SKU, like Standard_ZRS. For example:

   az storage account create \
     --name <STORAGE_NAME> \
     --location <REGION> \
     --resource-group <RESOURCE_GROUP> \
     --sku Standard_ZRS \
     --allow-blob-public-access false
   

2. When creating the Premium plan, add the --zone-redundant true parameter:

   az functionapp plan create \
     --resource-group <RESOURCE_GROUP> \
     --name <PLAN_NAME> \
     --location <REGION> \
     --sku EP1 \
     --zone-redundant true
   

3. Create the function app and associate it with the zone-redundant Premium plan:

   az functionapp create \
     --resource-group <RESOURCE_GROUP> \
     --name <APP_NAME> \
     --storage-account <STORAGE_NAME> \
     --plan <PLAN_NAME> \
     --runtime <RUNTIME> \
     --runtime-version <RUNTIME_VERSION>
   

You can use a Bicep file to deploy to a zone-redundant Premium plan. To learn how to deploy function apps to a Premium plan, see Automate resource deployment in Azure Functions.

The only properties to be aware of while creating a zone-redundant hosting plan are the zoneRedundant property and the plan's instance count (capacity) fields. The zoneRedundant property must be set to true and the capacity property should be set based on the workload requirement, but not less than 3. Choosing the right capacity varies based on several factors and high availability / fault tolerance strategies. A good rule of thumb is to specify sufficient instances for the application to ensure that losing one zone instance leaves sufficient capacity to handle expected load.

Following is a Bicep template snippet for a zone-redundant, Premium plan. It shows the zoneRedundant field and the capacity specification.

resource EPFuncPlan 'Microsoft.Web/serverfarms@2024-04-01' = {
    name: '<YOUR_PLAN_NAME>'
    location: '<YOUR_REGION_NAME>'
    sku: {
        name: 'EP1'
        tier: 'ElasticPremium'
        size: 'EP1'
        family: 'EP'
        capacity: 3
    }
    kind: 'elastic'
    properties: {
        perSiteScaling: false
        elasticScaleEnabled: true
        maximumElasticWorkerCount: 20
        isSpot: false
        reserved: false
        isXenon: false
        hyperV: false
        targetWorkerCount: 0
        targetWorkerSizeId: 0
        zoneRedundant: true
    }
}

To learn more about these templates, see Automate resource deployment in Azure Functions.

You can use an ARM template to deploy to a zone-redundant Premium plan. To learn how to deploy function apps to a Premium plan, see Automate resource deployment in Azure Functions.

The only properties to be aware of while creating a zone-redundant hosting plan are the zoneRedundant property and the plan's instance count (capacity) fields. The zoneRedundant property must be set to true and the capacity property should be set based on the workload requirement, but not less than 3. Choosing the right capacity varies based on several factors and high availability / fault tolerance strategies. A good rule of thumb is to specify sufficient instances for the application to ensure that losing one zone instance leaves sufficient capacity to handle expected load.

Following is an ARM template snippet for a zone-redundant, Premium plan. It shows the zoneRedundant field and the capacity specification.

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
        "type": "Microsoft.Web/serverfarms",
        "apiVersion": "2024-04-01",
        "name": "<YOUR_PLAN_NAME>",
        "location": "<YOUR_REGION_NAME>",
        "sku": {
            "name": "EP1",
            "tier": "ElasticPremium",
            "size": "EP1",
            "family": "EP", 
            "capacity": 3
        },
        "kind": "elastic",
        "properties": {
            "perSiteScaling": false,
            "elasticScaleEnabled": true,
            "maximumElasticWorkerCount": 20,
            "isSpot": false,
            "reserved": false,
            "isXenon": false,
            "hyperV": false,
            "targetWorkerCount": 0,
            "targetWorkerSizeId": 0, 
            "zoneRedundant": true
        }
    }
  ]
}

To learn more about these templates, see Automate resource deployment in Azure Functions.

1. In the Azure portal, search for and select the function app to update.

2. Under Settings, select Scale and Concurrency.

3. On the Zone redundancy tab, check Add zone redundancy to enable the feature. If already checked, you can uncheck this box to disable the feature.

4. Select Save to commit your changes and restart the app.

Update the app by using the --zone-redundant parameter of the az functionapp plan update command. Use a value of true to enable zone redundancy and false disable the feature. This example enables zone redundancy for an existing app in a Flex Consumption plan:

PLAN_RESOURCE_ID=$(az functionapp show --resource-group <RESOURCE_GROUP> --name <APP_NAME> --query "properties.serverFarmId"  -o tsv) 

az functionapp plan update --ids $PLAN_RESOURCE_ID --set zoneRedundant=true

In this example, replace <RESOURCE_GROUP> and <APP_NAME> with the names of your resource group and app, respectively.

You can use this Bicep file to add the zoneRedundant property to true in an existing plan definition:

resource existingServerFarm 'Microsoft.Web/serverfarms@2024-04-01' existing = {
  name: '<YOUR_PLAN_NAME>'
  scope: resourceGroup()
}

resource updatedServerFarm 'Microsoft.Web/serverfarms@2024-04-01' = {
  name: existingServerFarm.name
  location: '<YOUR_REGION_NAME>'
  kind: 'functionapp'
  sku: {
    tier: 'FlexConsumption'
    name: 'FC1'
  }
  properties: {
    reserved: true
    zoneRedundant: true  // Enables zone redundancy
  }
}

In this file, replace <YOUR_PLAN_NAME> and <YOUR_REGION_NAME> with the name of your plan and region, respectively. To learn how to deploy a Bicep file, see Deploy your template.

You can use this ARM template fragment to set the zoneRedundant property to true in an existing plan definition:

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Web/serverfarms",
      "apiVersion": "2024-04-01",
      "name": "<YOUR_PLAN_NAME>",
      "location": "<YOUR_REGION_NAME>",
      "kind": "functionapp",
      "sku": {
        "tier": "FlexConsumption",
        "name": "FC1"
      },
      "properties": {
        "reserved": true,
        "zoneRedundant": true
      }
    }
  ]
}

In this template, replace <YOUR_PLAN_NAME> and <YOUR_REGION_NAME> with the name of your plan and region, respectively. To learn how to deploy an ARM template, see Deploy your template.