Using the IRDMA RDMA driver

Cloud RDMA enables low-latency reliable messaging capabilities by using the IRDMA RDMA driver. This driver supports Remote Direct Memory Access (RDMA) between Compute Engine instances. RDMA transfers data between remote machines and local memory through the network interface without using host CPU or intermediate host buffers.

RDMA capable instances require at least two virtual network interfaces (vNICs):

  • A vNIC for RDMA communication that uses the IDPF network and IRDMA RDMA driver. This vNIC can't connect to the internet. An instance can have only one vNIC that uses IRDMA.
  • A vNIC for normal network traffic. This vNIC is fully connected to the Google Cloud network can connect to the internet. This vNIC uses the gVNIC network driver. You can add up to eight additional GVNIC network interfaces, for a total of 10 NICs per instance.

The IRDMA network driver is supported with H4D instances.

When configuring a vNIC that uses the IRDMA driver, you must specify a VPC network that was created by using the Falcon RDMA network profile.

Before you begin

  • 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.

    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. 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.

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

Operating system support

During the preview period, use the HPC VM image, which comes with Cloud RDMA drivers pre-installed.

Overview of using IRDMA with Compute Engine instances

To create a compute instance that uses Cloud RDMA, you must have at least one regular VPC network and one Falcon VPC network. The Falcon VPC network uses an RDMA network profile that enables RDMA traffic between H4D instances. This network is separate from the regular VPC network that carries non-RDMA traffic to other Google Cloud services or the internet.

The tasks to complete to create a compute instance that uses Cloud RDMA are as follows:

  1. Choose a public OS image that supports IRDMA, or create a custom OS image that is tagged to use IRDMA.

  2. Identify or create at least two VPC networks:

    • A regular VPC network for the traffic that goes through the gVNIC network interface
    • A Falcon VPC network for the RDMA traffic

  3. Create a compute instance using the public or custom OS image. During the instance creation, configure at least two network interfaces: one that uses the gVNIC driver and one that uses the IRDMA driver.

  4. Verify that IRDMA is enabled.

Create a custom OS image that supports IRDMA

You can create the OS image using either the Google Cloud CLI or REST. For detailed information and best practices for creating custom OS images, see Create custom OS images.

gcloud

  1. Select an OS image or image family that supports IRDMA. During the preview period, use the HPC VM image.

  2. Using the OS image or image family selected in the previous step, create a custom OS image. To create the custom OS image, use the gcloud compute images create command. For example, the following command creates a custom OS image that supports IRDMA and is based on a specific OS image.

    gcloud compute images create IMAGE_NAME \
    --source-image=SOURCE_IMAGE \
    --source-image-project=SOURCE_IMAGE_PROJECT \

    Replace the following:

    • IMAGE_NAME: the name of the image that you want to create

    • SOURCE_IMAGE: a specific OS image that supports IRDMA—for example: hpc-rocky-linux-8-v20250721

      If you want to use the latest OS image in an image family, replace the --source-image flag with the --source-image-family flag and set its value to an image family that supports IRDMA. For example: --source-image-family=hpc-rocky-linux-8.

    • SOURCE_IMAGE_PROJECT: the name of the project that contains the source OS image or image family

    For more information about when to use image families, see Image family best practices.

REST

  1. Select an OS image or image family that supports IRDMA For more information, see Operating system details.

  2. Using the OS image or image family selected in the previous step, create an OS image by using the images.insert method.

    POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/global/images
{
  "name":"IMAGE_NAME",
  "sourceImage":"SOURCE_IMAGE_URI"
}

    Replace the following:

    • PROJECT_ID: the ID of the project in which to create the new image
    • IMAGE_NAME: a name for the custom image

    • SOURCE_IMAGE_URI: the URI for the specific OS image or image family that you want to use

      For example:

      • Specific OS image: "sourceImage": "projects/rocky-linux-cloud/global/images/hpc-rocky-linux-8-v20250721"
      • Image family: "sourceImage": "projects/rocky-linux-cloud/global/images/family/hpc-rocky-linux-8"

      When you specify an image family, Compute Engine creates a VM from the most recent, non-deprecated OS image in that family. For more information about when to use image families, see Image family best practices.

Create a VM with IRDMA support

You can create a VM using one of the supported public OS images or using a custom OS image you created using the steps in Create a custom OS image that supports IRDMA.

To use RDMA with your instance, you must configure multiple network interfaces (NICs) for the instance. One NIC must use the GVNIC driver (specify nic-type=GVNIC) and another NIC must use the IRDMA driver (specify nic-type=IRDMA).

Create a VM using a public OS image

To create VMs using the HPC VM image, or a public OS image that supports IRDMA, follow the instructions on the following pages:

Create a VM using a custom OS image

If you aren't using a public OS image that supports IRDMA, you must first create a custom OS image that supports IRDMA. You then use that custom OS image to create a VM by using the Google Cloud console, Google Cloud CLI, or REST.

For instructions on how to create an instance using a custom image, see Create an instance from a custom image.

Verify that IRDMA is enabled

After the VM is deployed, run the following performance bandwidth test to ensure that you are running on a healthy RDMA-enabled VM instance.

ib_send_bw -aF & # start the server
ib_send_bw -aF $(hostname) # start the client (can be done on the same machine)

The reported single-connection bandwidth BW average [MB/s] should reach at least 11,000 MB/s for rows higher than 4096B; smaller values are expected for lower message sizes.

What's next