Create an AI-optimized MIG with A4X

This document describes how to create a managed instance group (MIG) that usesA4X machine type. To learn more about the machine type, seeA4X seriesin the Compute Engine documentation.

Create a MIG if you want to manage multiple virtual machines (VMs) as a singleentity. To learn more about MIGs, seeManaged instance groupsin the Compute Engine documentation.

To learn about VM and cluster creation options, seeDeployment options overviewpage.

Limitations

When you create a MIG with A4X VMs, the following limitations apply:

  • If you create a regional MIG, then the MIG can only create VMs in thezone that contains yourVPC network's profile.

  • You can't configureinstance flexibilityin the MIG.

  • If you apply a workload policy to a MIG, you cannot changethe policy in the MIG when the group has VMs in it. To change the policy in aMIG that has VMs, you must firstresizethe MIG to zero.

  • You can't use an instance template that specifies a placement policy to createa MIG that uses a workload policy.

  • You must use thereservation-boundprovisioning model. Other provisioning models are not supported.

  • You can't use a resize request to add VMs to the MIG. You must set the targetsize of the MIG to add VMs.

Before you begin

Before creating a MIG, if you haven't already done so, complete the followingsteps:

  1. Choose a consumption option: your choice of consumption option determines how you get and use GPU resources.

    To learn more, seeChoose a consumption option.

  2. Obtain capacity: the process to obtain capacity differs for each consumption option.

    To learn about the process to obtain capacity for your chosen consumption option, seeCapacity overview.

    Note: When you request A4X capacity, you obtain it in theall capacity mode. This mode is the only supported reservation operational mode for A4X machine types. For more information about all capacity mode, seeReservation operational mode.

Required roles

To get the permissions that you need to create a MIG, ask your administrator to grant you theCompute Instance Admin (v1) (roles/compute.instanceAdmin.v1) IAM role on the project. For more information about granting roles, seeManage access to projects, folders, and organizations.

This predefined role contains the permissions required to create a MIG. To see the exact permissions that are required, expand theRequired permissions section:

Required permissions

The following permissions are required to create a MIG:

  • To create a MIG: compute.instanceGroupManagers.create on the project

You might also be able to get these permissions withcustom roles or otherpredefined roles.

A4X fundamentals

An A4X cluster is organized into a hierarchy of blocks and subblocks to facilitate large-scale,non-blocking network performance. Understanding this topology is key when reserving capacity anddeploying workloads.

A4X instance
An A4X instance is a single A4X machine type that has 4 GPUs attached.
NVLink domain or subblock
An NVLink domain, also referred to as a subblock, is the fundamental unit of A4X capacity. AnNVLink domain consists of 18 A4X instances (72 GPUs) connected using amulti-node NVLinksystem. You create an A4X NVLink domain or a subblock by applying a workload policy that specifies a1x72 topology.
Block
An A4X block is composed of 25 subblocks (NVLink domains), totalling up to 450 A4X instances(1,800 GPUs). The subblocks are rail-aligned for efficient scaling. Each subblock requires aMIG.Therefore, for a single A4X block, you can create 25MIGs.

The following table shows the supported topology options for A4X instances:

Topology (acceleratorTopology)Number of GPUsNumber of instances
1x727218

Overview

Creating a MIG with the A4X machine type includes the following steps:

  1. Create VPC networks
  2. Create a workload policy
  3. Create an instance template
  4. Create a MIG

Create VPC networks

Tip: If you are setting up a quick test, you can skip this step and specify a single NIC--network-interface=nic-type=GVNIC instead.

To set up the network for A4X machine type, create three VPC networks for the following network interfaces:

  • 2 regular VPC networks for thegVNIC network interfaces (NIC). These are used for host to host communication.
  • 1 VPC network with theRoCE network profile is required for the CX-7 NICs when creating multiple A4X subblocks. The RoCE VPC network needs to have 4 subnets, one subnet for each CX-7 NIC. These NICs use RDMA over Converged Ethernet (RoCE), providing the high-bandwidth, low-latency communication that's essential for scaling out to multiple A4X subblocks. For a single A4X subblock, you can skip this VPC network because within a single subblock, direct GPU to GPU communication is handled by the multi-node NVLink.

For more information about NIC arrangement, seeReview network bandwidth and NIC arrangement.

Create the networks either manually by following the instruction guides or automatically by usingthe provided script.

Instruction guides

To create the networks, you can use the following instructions:

For these VPC networks, we recommend setting themaximum transmission unit (MTU) to a larger value.For A4X machine type, the recommended MTU is8896 bytes.To review the recommended MTU settings for other GPU machine types, seeMTU settings for GPU machine types.

Script

To create the networks, follow these steps.

For these VPC networks, we recommend setting themaximum transmission unit (MTU) to a larger value.For A4X machine type, the recommended MTU is8896 bytes.To review the recommended MTU settings for other GPU machine types, seeMTU settings for GPU machine types.

  1. Use the following script to create regular VPC networks for the gVNICs.

          #!/bin/bash    # Create regular VPC networks and subnets for the gVNICs    for N in $(seq 0 1); do      gcloud compute networks createGVNIC_NAME_PREFIX-net-$N \        --subnet-mode=custom \        --mtu=8896      gcloud compute networks subnets createGVNIC_NAME_PREFIX-sub-$N \        --network=GVNIC_NAME_PREFIX-net-$N \        --region=REGION \        --range=192.168.$N.0/24      gcloud compute firewall-rules createGVNIC_NAME_PREFIX-internal-$N \        --network=GVNIC_NAME_PREFIX-net-$N \        --action=ALLOW \        --rules=tcp:0-65535,udp:0-65535,icmp \        --source-ranges=192.168.0.0/16    done    # Create SSH firewall rules    gcloud compute firewall-rules createGVNIC_NAME_PREFIX-ssh \      --network=GVNIC_NAME_PREFIX-net-0 \      --action=ALLOW \      --rules=tcp:22 \      --source-ranges=IP_RANGE    # Assumes that an external IP is only created for vNIC 0    gcloud compute firewall-rules createGVNIC_NAME_PREFIX-allow-ping-net-0 \      --network=GVNIC_NAME_PREFIX-net-0 \      --action=ALLOW \      --rules=icmp \      --source-ranges=IP_RANGE

  2. If you require multiple A4X subblocks, use the following script to create the RoCE VPC network and subnets for the four CX-7 NICs on each A4X instance.

    Important: If your deployment consists of only a single A4X subblock, you can skip this step.
          # List and make sure network profiles exist in the machine type's zone    gcloud compute network-profiles list --filter "location.name=ZONE"    # Create network for CX-7    gcloud compute networks createRDMA_NAME_PREFIX-mrdma \      --network-profile=ZONE-vpc-roce \      --subnet-mode custom \      --mtu=8896    # Create subnets    for N in $(seq 0 3); do      gcloud compute networks subnets createRDMA_NAME_PREFIX-mrdma-sub-$N \        --network=RDMA_NAME_PREFIX-mrdma \        --region=REGION \        --range=192.168.$((N+2)).0/24 & # offset to avoid overlap with gVNICs    done

    Replace the following:

  3. Optional: To verify that the VPC network resources are created successfully, check the network settings in the Google Cloud console:
    1. In the Google Cloud console, go to theVPC networks page.

      Go to VPC networks

    2. Search the list for the networks that you created in the previous step.
    3. To view the subnets, firewall rules, and other network settings, click the name of the network.

Create a workload policy

You cannot update a workload policy after you create it. To make changes in aworkload policy, you must create a new one.

To create a workload policy, select one of the following options:

gcloud

To create a workload policy, use thegcloud compute resource-policies create workload-policy command.

For inter-accelerator network configuration, specify the--accelerator-topologyflag in the command.

Use the following command for A4X machine type. The accelerator topology of1x72 indicates 72 GPUs connected via a NVLink within a block.

gcloud compute resource-policies create workload-policyWORKLOAD_POLICY_NAME \    --type=high-throughput \    --accelerator-topology=1x72 \    --region=REGION

Replace the following:

  • WORKLOAD_POLICY_NAME: the name of the workload policy.
  • REGION: the region where you want to create the workload policy.Specify a region in which you want to create the MIG and the machine type that you want touse is available. For information about regions, seeGPU availability by regions and zones.

REST

To create a workload policy, make aPOSTrequest to theresourcePolicies.insert method.

For inter-accelerator network configuration, specify theacceleratorTopologyfield in the request.

Make the following request for A4X machine type. The acceleratortopology of1x72 indicates 72 GPUs connected via a NVLink within a block.

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/resourcePolicies  {    "name": "WORKLOAD_POLICY_NAME"    "workloadPolicy": {      "type": "HIGH_THROUGHPUT",      "acceleratorTopology": "1x72"    }  }

Replace the following:

  • PROJECT_ID: your project ID
  • REGION: the region where you want to create the workload policy. Specify a region in which you want to create the MIG and the machine type that you want to use is available. For information about regions, seeGPU availability by regions and zones.
  • WORKLOAD_POLICY_NAME: the name of the workload policy.

Create an instance template

Specify the VM properties for a MIG by creating an instance template.

To create an instance template, select one of the following options.

The following commands also set the access scope for your instances. To simplify permissionsmanagement, Google recommends that you set the access scope on an instance tocloud-platform access and then use IAM roles to define what services the instance canaccess. For more information, seeScopes best practice.

gcloud

To create a regional instance template, use thegcloud compute instance-templates create command.

Important: The following example uses the networking setup for multiple subblocks. If you're creating only a single A4X subblock and you only created the gVNIC network in theCreate VPC networks step, then remove the four RDMA subnets indicated by theMRDMA NIC type from the example.

gcloud compute instance-templates createINSTANCE_TEMPLATE_NAME \    --machine-type=a4x-highgpu-4g \    --image-family=IMAGE_FAMILY \    --image-project=IMAGE_PROJECT \    --instance-template-region=REGION \    --boot-disk-type=hyperdisk-balanced \    --boot-disk-size=DISK_SIZE \    --scopes=cloud-platform \    --network-interface=nic-type=GVNIC,network=GVNIC_NAME_PREFIX-net-0,subnet=GVNIC_NAME_PREFIX-sub-0 \    --network-interface=nic-type=GVNIC,network=GVNIC_NAME_PREFIX-net-1,subnet=GVNIC_NAME_PREFIX-sub-1,no-address \    --network-interface=nic-type=MRDMA,network=RDMA_NAME_PREFIX-mrdma,subnet=RDMA_NAME_PREFIX-mrdma-sub-0,no-address \    --network-interface=nic-type=MRDMA,network=RDMA_NAME_PREFIX-mrdma,subnet=RDMA_NAME_PREFIX-mrdma-sub-1,no-address \    --network-interface=nic-type=MRDMA,network=RDMA_NAME_PREFIX-mrdma,subnet=RDMA_NAME_PREFIX-mrdma-sub-2,no-address \    --network-interface=nic-type=MRDMA,network=RDMA_NAME_PREFIX-mrdma,subnet=RDMA_NAME_PREFIX-mrdma-sub-3,no-address \    --reservation-affinity=specific \    --reservation=RESERVATION \    --provisioning-model=RESERVATION_BOUND \    --instance-termination-action=DELETE \    --maintenance-policy=TERMINATE

Replace the following:

  • INSTANCE_TEMPLATE_NAME: the name of the instance template.
  • IMAGE_FAMILY: the image family of the OS image that you want to use.For a list of supported operating systems, seeSupported operating systems.
  • IMAGE_PROJECT: the project ID of the OS image.
  • REGION: the region where you want to create the instance template.Specify a region in which the machine type that you want to use is available.For information about regions, seeGPU availability by regions and zones.
  • DISK_SIZE: the size of the boot disk in GB.
  • GVNIC_NAME_PREFIX: the name prefix that you specified when creating the standard VPC networks and subnets that use gVNIC NICs.
  • RDMA_NAME_PREFIX: the name prefix that you specified when creating the VPC networks and subnets that use RDMA NICs.
  • RESERVATION: the reservation name, a block, or a subblock within a reservation. To get the reservation name or the available blocks, seeView reserved capacity. Based on your requirements for instance placement, choose one of the following:
    • To create the instances on any single block:
          projects/RESERVATION_OWNER_PROJECT_ID/reservations/RESERVATION_NAME
    • To create the instances on a specific block:
          projects/RESERVATION_OWNER_PROJECT_ID/reservations/RESERVATION_NAME/reservationBlocks/RESERVATION_BLOCK_NAME
    • To create the instances in a specific subblock:
          projects/RESERVATION_OWNER_PROJECT_ID/reservations/RESERVATION_NAME/reservationBlocks/RESERVATION_BLOCK_NAME/reservationSubBlocks/RESERVATION_SUBBLOCK_NAME
    Tip: If the reservation exists in the current project, then you can omitprojects/RESERVATION_OWNER_PROJECT_ID/reservations/ from the reservation value.

REST

To create a regional instance template, make aPOST request to theregionInstanceTemplates.insert method.

Important: The following example uses the networking setup for multiple subblocks. If you're creating only a single A4X subblock and you only created the gVNIC network in theCreate VPC networks step, then remove the four RDMA subnets indicated by theMRDMA NIC type from the example.

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/instanceTemplates{  "name":"INSTANCE_TEMPLATE_NAME",  "properties":{    "machineType":"a4x-highgpu-4g",    "disks":[      {        "boot":true,        "initializeParams":{          "diskSizeGb":"DISK_SIZE",          "diskType":"hyperdisk-balanced",          "sourceImage":"projects/IMAGE_PROJECT/global/images/family/IMAGE_FAMILY"        },        "mode":"READ_WRITE",        "type":"PERSISTENT"      }    ],    "serviceAccounts": [      {        "email": "default",        "scopes": [          "https://www.googleapis.com/auth/cloud-platform"        ]      }    ],    "networkInterfaces": [      {        "accessConfigs": [          {            "name": "external-nat",            "type": "ONE_TO_ONE_NAT"          }        ],        "network": "projects/NETWORK_PROJECT_ID/global/networks/GVNIC_NAME_PREFIX-net-0",        "nicType": "GVNIC",        "subnetwork": "projects/NETWORK_PROJECT_ID/region/REGION/subnetworks/GVNIC_NAME_PREFIX-sub-0"      },      {        "network": "projects/NETWORK_PROJECT_ID/global/networks/GVNIC_NAME_PREFIX-net-1",        "nicType": "GVNIC",        "subnetwork": "projects/NETWORK_PROJECT_ID/region/REGION/subnetworks/GVNIC_NAME_PREFIX-sub-1"      },      {        "network": "projects/NETWORK_PROJECT_ID/global/networks/RDMA_NAME_PREFIX-mrdma",        "nicType": "MRDMA",        "subnetwork": "projects/NETWORK_PROJECT_ID/region/REGION/subnetworks/RDMA_NAME_PREFIX-mrdma-sub-0"      },      {        "network": "projects/NETWORK_PROJECT_ID/global/networks/RDMA_NAME_PREFIX-mrdma",        "nicType": "MRDMA",        "subnetwork": "projects/NETWORK_PROJECT_ID/region/REGION/subnetworks/RDMA_NAME_PREFIX-mrdma-sub-1"      },      {        "network": "projects/NETWORK_PROJECT_ID/global/networks/RDMA_NAME_PREFIX-mrdma",        "nicType": "MRDMA",        "subnetwork": "projects/NETWORK_PROJECT_ID/region/REGION/subnetworks/RDMA_NAME_PREFIX-mrdma-sub-2"      },      {        "network": "projects/NETWORK_PROJECT_ID/global/networks/RDMA_NAME_PREFIX-mrdma",        "nicType": "MRDMA",        "subnetwork": "projects/NETWORK_PROJECT_ID/region/REGION/subnetworks/RDMA_NAME_PREFIX-mrdma-sub-3"      }    ],    "reservationAffinity":{        "consumeReservationType":"SPECIFIC_RESERVATION",        "key":"compute.googleapis.com/reservation-name",        "values":[          "RESERVATION"        ]      },    "scheduling":{        "provisioningModel":"RESERVATION_BOUND",        "instanceTerminationAction":"DELETE",        "onHostMaintenance": "TERMINATE",        "automaticRestart":true      }  }}

Replace the following:

  • INSTANCE_TEMPLATE_NAME: the name of the instance template.
  • IMAGE_FAMILY: the image family of the OS image that you want to use. For a list of supported operating systems, seeSupported operating systems.
  • IMAGE_PROJECT: the project ID of the OS image.
  • REGION: the region where you want to create the instance template. Specify a region in which the machine type that you want to use is available. For information about regions, seeGPU availability by regions and zones.
  • DISK_SIZE: the size of the boot disk in GB.
  • NETWORK_PROJECT_ID: the project ID of the network.
  • GVNIC_NAME_PREFIX: the name prefix that you specified when creating the standard VPC networks and subnets that use gVNIC NICs.
  • REGION: the region of the subnetwork.
  • RDMA_NAME_PREFIX: the name prefix that you specified when creating the VPC networks and subnets that use RDMA NICs.
  • RESERVATION: the reservation name, a block, or a subblock within a reservation. To get the reservation name or the available blocks, seeView reserved capacity. Based on your requirements for instance placement, choose one of the following:
    • To create the instances on any single block:
          projects/RESERVATION_OWNER_PROJECT_ID/reservations/RESERVATION_NAME
    • To create the instances on a specific block:
          projects/RESERVATION_OWNER_PROJECT_ID/reservations/RESERVATION_NAME/reservationBlocks/RESERVATION_BLOCK_NAME
    • To create the instances in a specific subblock:
          projects/RESERVATION_OWNER_PROJECT_ID/reservations/RESERVATION_NAME/reservationBlocks/RESERVATION_BLOCK_NAME/reservationSubBlocks/RESERVATION_SUBBLOCK_NAME
    Tip: If the reservation exists in the current project, then you can omitprojects/RESERVATION_OWNER_PROJECT_ID/reservations/ from the reservation value.

Create a MIG

When you use an A4X machine type, you must create a MIG by specifying its targetsize.

To obtain a GPU topology of1x72, create a MIG with 18 instances. When you create the MIG, apply the workload policy that specifies theacceleratorTopology field. Applying the policy ensures that Compute Engine creates all 18 instances in one subblock to use an NVLink domain. If a subblock lacks capacity for all 18 instances, then anymanaged instance that can't be created immediately will remain inCREATING state until capacity becomes available. These managed instances represent the VMs that the MIG creates when there is capacity.

When you apply a workload policy with theacceleratorTopology field set to1x72, you cannot create more than 18 instances in a MIG. Specifying more than 18 instances causes the MIG creation to fail. To create multiple NVLink domains, create a separate MIG for each domain and apply the same workload policy to each MIG.

To create a MIG, select one of the following options:

gcloud

To create a MIG with a specified target size, use theinstance-groups managedcreate command.

Create a zonal or regional MIG as follows:

  • To create a zonal MIG, use the following command:
    gcloud compute instance-groups managed createMIG_NAME \  --template=INSTANCE_TEMPLATE_URL \  --size=TARGET_SIZE \  --workload-policy=WORKLOAD_POLICY_URL \  --zone=ZONE
  • To create a regional MIG, use the following command:
    gcloud compute instance-groups managed createMIG_NAME \    --template=INSTANCE_TEMPLATE_URL \    --size=TARGET_SIZE \    --workload-policy=WORKLOAD_POLICY_URL \    --region=REGION
Replace the following:
  • MIG_NAME: the name of the MIG.
  • INSTANCE_TEMPLATE_URL: the URL of the instance template that you want touse to create VMs in the MIG. The URL can contain either theIDor name of the instance template. Specify one of the following values:
    • For a regional instance template:projects/PROJECT_ID/regions/REGION/instanceTemplates/INSTANCE_TEMPLATE_ID
    • For a global instance template:INSTANCE_TEMPLATE_ID
  • TARGET_SIZE: the number of VMs that you want in the MIG. For the accelerator topology of1x72, set the target size to18.
  • WORKLOAD_POLICY_URL: the URL of the workload policy. For example,projects/example-project/regions/us-central1/resourcePolicies/example-workload-policy.
  • ZONE: the zone in which you want to create the MIG. Specify a zone within the workload policy's region.
  • REGION: the region in which you want to create the MIG. Specify the same region as that of the workload policy. For a regional MIG, instead of a region, you can specify the zones in that region by using the--zones flag.

REST

To create a MIG with a specified target size, make aPOST request.

Create a zonal or regional MIG as follows:

  • To create a zonal MIG, make aPOST request to theinstanceGroupManagers.insert method.
    POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instanceGroupManagers{  "versions": [    {      "instanceTemplate": "INSTANCE_TEMPLATE_URL"    }  ],  "name": "MIG_NAME",  "instanceTemplate": "INSTANCE_TEMPLATE_URL",  "targetSize": "TARGET_SIZE",  "resourcePolicies": {    "workloadPolicy":WORKLOAD_POLICY_URL  }}
  • To create a regional MIG, make aPOST request to theregionInstanceGroupManagers.insert method.
      POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/instanceGroupManagers  {    "versions": [      {        "instanceTemplate": "INSTANCE_TEMPLATE_URL"      }    ],    "name": "MIG_NAME",    "instanceTemplate": "INSTANCE_TEMPLATE_URL",    "targetSize": "TARGET_SIZE",    "resourcePolicies": {      "workloadPolicy":WORKLOAD_POLICY_URL    }  }
Replace the following:
  • PROJECT_ID: the project ID.
  • ZONE: the zone in which you want to create the MIG. Specify a zone within the workload policy's region.
  • REGION: the region in which you want to create the MIG. Specify the same region as that of the workload policy.
  • INSTANCE_TEMPLATE_URL: the URL of the instance template that you want touse to create VMs in the MIG. The URL can contain either theIDor name of the instance template. Specify one of the following values:
    • For a regional instance template:projects/PROJECT_ID/regions/REGION/instanceTemplates/INSTANCE_TEMPLATE_ID
    • For a global instance template:INSTANCE_TEMPLATE_ID
  • MIG_NAME: the name of the MIG.
  • TARGET_SIZE: the number of VMs that you want in the MIG. For the accelerator topology of1x72, set the target size to18.
  • WORKLOAD_POLICY_URL: the URL of the workload policy. For example,projects/example-project/regions/us-central1/resourcePolicies/example-workload-policy.

What's next?

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Last updated 2025-12-15 UTC.