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Create a MIG with stateful disks

This document describes how to create a managed instance group (MIG) that preserves the data on disks with a given device name for all of the MIG's VMs, even in the event of VM recreation—for example when a VM in the MIG is autohealed, updated, or recreated. Preserving disks is useful for certain workloads—for example, for databases or legacy applications.

In addition to preserving disks for all VMs in the group, you can also configure a stateful MIG for the following:

• You can add and preserve instance-specific disks.
• You can add and preserve instance-specific metadata.
• You can add and preserve IP addresses.

For more information, see the stateful MIG overview.

You can also read about other basic scenarios for creating a MIG.

Before you begin

• Create an instance template, which is required in order to create a managed instance group.
• If you haven't already, set up authentication. Authentication verifies your identity for access to Google Cloud services and APIs. To run code or samples from a local development environment, you can authenticate to Compute Engine by selecting one of the following options:

  Select the tab for how you plan to use the samples on this page:

  Console

  When you use the Google Cloud console to access Google Cloud services and APIs, you don't need to set up authentication.

  gcloud

  1. Install the Google Cloud CLI. After installation, initialize the Google Cloud CLI by running the following command:

     gcloud init

     If you're using an external identity provider (IdP), you must first sign in to the gcloud CLI with your federated identity.

  2. Set a default region and zone.

  Terraform

  To use the Terraform samples on this page in a local development environment, install and initialize the gcloud CLI, and then set up Application Default Credentials with your user credentials.

  1. Install the Google Cloud CLI.

  2. If you're using an external identity provider (IdP), you must first sign in to the gcloud CLI with your federated identity.

  3. If you're using a local shell, then create local authentication credentials for your user account:

     gcloud auth application-default login

     You don't need to do this if you're using Cloud Shell.

     If an authentication error is returned, and you are using an external identity provider (IdP), confirm that you have signed in to the gcloud CLI with your federated identity.

  For more information, see Set up authentication for a local development environment.

  REST

  To use the REST API samples on this page in a local development environment, you use the credentials you provide to the gcloud CLI.

  Install the Google Cloud CLI.

  If you're using an external identity provider (IdP), you must first sign in to the gcloud CLI with your federated identity.

  For more information, see Authenticate for using REST in the Google Cloud authentication documentation.

Limitations

A MIG with stateful configuration—a stateful MIG—has the following limitations:

• You cannot use autoscaling if your MIG has stateful configuration.
• If you want to use automated rolling updates, you must set the replacement method to RECREATE.
• For stateful regional MIGs, you must disable proactive redistribution (set the redistribution type to NONE) to prevent deletion of stateful instances by automatic cross-zone redistribution.
• If you use an all-instances configuration to override instance template properties, you cannot specify those properties in any per-instance configuration and at the same time in the group's all-instances configuration.

To see the full list of MIG limitations, which varies based on the configuration that you use, see MIG limitations.

Create a MIG with stateful disks

Use the Google Cloud console, the gcloud CLI, Terraform, or REST.

gcloud compute instance-groups managed create INSTANCE_GROUP_NAME \
    --template INSTANCE_TEMPLATE_URL \
    --size SIZE \
    --stateful-disk device-name=DEVICE_NAME[,auto-delete=DELETE_RULE]

resource "google_compute_instance_group_manager" "default" {
  name               = "igm-stateful-disk-basic"
  zone               = "us-central1-f"
  base_instance_name = "instance"
  target_size        = 1

  version {
    instance_template = google_compute_instance_template.default.id
  }

  stateful_disk {
    device_name = "example-disk"
    delete_rule = "NEVER"
  }

}

POST https://compute.googleapis.com/compute/v1/projects/PROJECT/zones/ZONE/instanceGroupManagers

{
  "name": "NAME",
  "versions": [
    {
      "instanceTemplate": "INSTANCE_TEMPLATE_URL"
    }
  ],
  "targetSize": SIZE,
  "statefulPolicy": {
    "preservedState": {
      "disks": {
        "DEVICE_NAME": {"autoDelete": "DELETE_RULE" },
        "DEVICE_NAME": {"autoDelete": "DELETE_RULE" }
      }
    }
  }
}