Amanaged instance group (MIG)is a group of virtual machine (VM) instances that you treat as a single entity.Each VM in a MIG is based on aninstance template.

If you only need to create multiple VMs, but don't want them grouped together ina MIG, see thebulk instance API.

To learn about other Compute Engine options, seeChoose a Compute Engine deployment strategy for your workload.

To get started with creating a MIG, read this document to find a basicconfiguration that works for you.

Basic scenarios for creating a MIG

MIGs have many configuration options. See the following guides to quickly get aMIG up and running for various scenarios:

• By default, you can create up to 1,000 VMs in a zonal MIG. If you need more,use one of the following options:

  • Increase the size limit of your MIG.
  • Create a regional MIG,which allows twice as many VMs as a zonal MIG.
  • Create multiple MIGs and split your workload across them.
  • Contact support to make a request.

• When updating a MIG, you can specify up to 1,000 VMs in a single request.

• Once the MIG is created, you cannot change its networks or subnetworks.All VMs in the MIG are assigned to the same subnetworks.

• Shared VPC on interfaces other thannic0 for managed instancegroups is supported in gcloud CLI and the API, but not inGoogle Cloud console.

A MIG that is spread across multiple zones—aregional MIG—has the followinglimitations:

• By default, you can create up to 2,000 VMs. If you need more,increase the size limit of your MIGorcontact support.
• You must select whichzonesare associated with a regional MIG when you create the MIG. After you choosespecific zones during creation, you cannot change or update the zones later.But you can set the MIG'starget distribution shapeto specify how the group distributes its managed instances across the zonesthat you selected.
• If you set the group's target distribution shape toBALANCED,ANY,orANY_SINGLE_ZONE, review thetarget distribution shape limitations.

• Load balancingwith a regional MIG doesn't support themax-rate target capacity inRATEandUTILIZATION balancing modes. To learn more about the usage guidelinesfor each load balancer, seeBalancing modes and target capacity settings.

A MIG withstateful configuration—astateful 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 thereplacement methodtoRECREATE.
• For stateful regional MIGs, you mustdisable proactive redistribution (set the redistribution type toNONE) to prevent deletion of statefulinstances by automatic cross-zone redistribution.
• If you use anall-instances configurationto override instance template properties, you cannot specify those propertiesin any per-instance configuration and at the same time in the group'sall-instances configuration.

If you want to configure an autoscaler for your MIG, review theautoscaler specifications, too.

IPv6 support

If you want your MIG to include VM instances that use IPv6addressing, you must use either the IPv6-only or the dual-stack settingwhen you create your instance template

Including instances with IPv6 addresses in a MIG has the following limitations:

• While you can useautohealing with dual-stack instances in a MIG, thehealth checking endpoint supports only IPv4.
• When using IPv6-only instances in a MIG, the following features aren'tsupported:
  • Health checking and autohealing
  • Stateful IP addresses
  • Target pools

For more information, seeCreate an instance template with IPv6 addresses.

Additional MIG tasks

After you've created a MIG, you might want to do the following:

Learn about the group and its VMs

• View info about your MIG and its managed VM instances
• Learn what a managed instance isand how to work with managed instances

Resize the group

• Add or remove VMsfrom the group

  • Automatically resize a MIG based on increases or decreases in load by configuring an autoscaler
  • Manually set the size of a MIG
  • Disable creation retries mode during resize
  • Create instances with specific names in a MIG
  • Delete specific instances from a group
  • Abandon instances from a group

• Increase the group's size limit

• Delete the group

Change the group's VM configuration

• Change the instance template for the group

• Apply configuration updates to the VMs in a MIG

  • Automatically apply configuration updates to VMs in a MIG
  • Selectively apply configuration updates to specific VMs

  • Understand theinstanceTemplate andversions fields

  • Recreate instances in the group

  • Canary test a new instance template in a MIG

• Learn how to add stateful configuration in order to preserve disks, IP addresses, and metadata when VMs are recreated

Add MIG features

• Set up an application-based health checkto automatically recreate VMs if your application does not respond asexpected
• Set up a load balancerto distribute user traffic across multiple instances of your application

Tutorials

Try a tutorial:

• Use autohealing for highly available applications
• Use load balancing for highly available applications
• Use autoscaling for highly scalable applications
• Migrate an existing workload to a stateful managed instance group