Changing the Machine Type of a Stopped Instance

You can change the machine type of a stopped instance if it is not part of a managed instance group. If you need to change the machine type of instances within a managed instance group, read Updating managed instance groups.

Change the machine types of your instances if your existing machine type is not a good fit for the workloads you run on that instance. You can change the machine type of an instance to adjust the number of vCPUs and memory as your workload changes. For example, you can start an instance with a smaller machine during setup, development, and testing and change the instance to use a larger machine type when you are ready for production workloads.

To learn about what machine types are available, read the Machine Types documentation.

Before you begin

If you want to use the command-line examples in this guide:
1. Install or update to the latest version of the gcloud command-line tool.
2. Set a default region and zone.
If you want to use the API examples in this guide, set up API access.
Understand how to stop an instance.
Understand machine types.

Permissions required for this task

To perform this task, you must have the following permissions.

compute.instances.setMachineType on the instance

Changing a machine type

For instances that are not part of a managed instance group, you can change the machine type without affecting the instance's persistent disk data (including installed applications and application data), SSH keys, or other instance configurations such as instance metadata. If your instance uses an ephemeral external IP address, there is a possibility that the IP address might change. To keep the IP address from changing, promote it to a static external IP address.

To change the machine type of a stopped instance, use the Google Cloud Console, the setMachineType method in the API, or the instances set-machine-type command in gcloud. You can only change the machine type of a stopped instance and an instance is considered stopped only when the instance is in the TERMINATED state. It is not possible to change the machine type of a running instance.

Console

Go to the VM Instances page.
In the Name column, click the name of the instance for which you want to change machine types.
From the instance details page, complete the following steps:
1. Click the Stop button to stop the instance, if you have not stopped it yet.
2. After the instance stops, click the Edit button at the top of the page.
3. Under the Machine configuration section, select the machine type you want to use, or create a custom machine type.
4. Save your changes.

gcloud

To change a machine type in gcloud, run the following command, replacing INSTANCE with the instance name, and MACHINE-TYPE with the desired machine type:

gcloud compute instances set-machine-type INSTANCE --machine-type MACHINE-TYPE

Your machine type can be a predefined machine type, such as n1-standard-1, or a custom machine type. For example, a custom machine type with 4 vCPUs and 1 GB of memory can be specified as:

--machine-type custom-4-1024

API

In the API, make a POST request with the desired machine type in the request body:

POST https://compute.googleapis.com/compute/v1/projects/PROJECT/zones/ZONE/instances/INSTANCE/setMachineType

{
    machineType: "zones/us-central1-f/machineTypes/n1-standard-1"
}

To declare a custom machine type, use the format:

zones/ZONE/machineTypes/custom-CPU-MEMORY

For example, this machine type has 4 vCPUs and 1 GB of memory:

zones/us-central1-f/machineTypes/custom-4-1024

Moving to a smaller machine type

If you move from a machine type with more resources to a machine type with fewer resources, such as moving from a n1-standard-8 machine type to a n1-standard-2, you could run into hardware resource issues or performance limitations because smaller machine types are less powerful than larger machine types. Make sure that your new machine type is able to support any applications or services that are currently running on the instance, or that you update your services and applications to run on the smaller machine types.

Billing implications

Each machine type is billed at a different rate, so make sure you understand the pricing implications of changing machine types. For example, an n1-standard-1 machine type costs more than an f1-micro machine type.

Changing a machine type might also affect the sustained use discounts for that VM. Sustained use discounts are calculated separately for different categories in the same region. If you change machine types so that the new machine type is in a different category, the subsequent running time of the virtual machine instance counts toward the sustained use discount of the new category.

For example, assume you have an instance with n1-standard-1 machine type running for half a month. You then decide to change the machine type to m1-ultramem-40. Once you make that change, Compute Engine starts counting the running time of the virtual machine instance towards the sustained use discount of the memory-optimized vCPU and memory category.

On your bill, you would see a sustained use discount applied to the n1-standard-1 machine type from before you made the machine type change, and a separate sustained use discount for m1-ultramem-40, if your instance remains running on m1-ultramem-40 for at least a 25% of the rest of the month.

Best practices

It is good practice to make regular backups of your persistent disk data using snapshots. Consider taking a snapshot of your persistent disk data before you change the machine type. If you want to make sure the new machine type is able to support the data on the existing virtual machine instance, you can take a persistent disk snapshot and use it to start a second virtual machine instance with the new machine type to confirm that the instance will start up successfully.

If you have a second persistent disk attached to your instance, make sure it is added to the /etc/fstab file so that it is automatically mounted when the instance reboots.