Dedicated Virtual Machine Hosts

Shapes and capacity: When you create a dedicated virtual machine host, you select a shape for the dedicated virtual machine host. The shape determines how much capacity is available and what types of instances can be launched on the host. Note that there is a difference between the number listed for billed OCPUs compared to available OCPUs. This is because some OCPUs are reserved for virtual machine management.

When you launch an instance on a dedicated virtual machine host, you can choose any of the VM shapes that are supported for that host.

You can mix VM instances with different supported shapes on the same dedicated virtual machine host. The size of each instance might impact the maximum number of instances that you can place on the dedicated virtual machine host. For more information, see Optimizing Capacity on a Dedicated Virtual Machine Host.

Billing: You are billed for the dedicated virtual machine host as soon as you create it, but you are not billed for any of the individual VM instances you place on it. You will still be billed for image licensing costs if they apply to the image you are using for the VM instances.

Supported features: Most of the Compute features for VM instances are supported for instances running on dedicated virtual machine hosts. However, the following features are not supported:

• Autoscaling
• Burstable instances
• Capacity reservations
• Changing the shape of an instance
• Confidential computing
• Instance pools
• Reboot migration, live migration, and rebuild-in-place infrastructure maintenance. You can use manual migration instead.

For administrators: The simplest policy to enable users to work with dedicated virtual machine hosts is listed in Let users manage Compute dedicated virtual machine hosts. It gives the specified group access to launch instances on dedicated virtual machine hosts and manage dedicated virtual machine hosts.

See Let users launch Compute instances on dedicated virtual machine hosts for an example of a policy that allows users to launch instances on dedicated virtual machine hosts without giving them full administrator access to dedicated virtual machine hosts.

To fully meet requirements for some compliance scenarios, you might be required to validate that your instances are running on a dedicated virtual machine host and not using shared infrastructure. The Oracle Cloud Infrastructure Audit service provides you with the functionality to do this. Use the steps described in Viewing Audit Log Events to access the log events for the dedicated virtual machine host.

The section on searching log events walks you through how to retrieve the log events with the data you need to verify that your instances are running on a dedicated virtual machine host. For this procedure:

• Ensure that you select the dedicated virtual machine host's compartment and not the compartment for the instances that are hosted on it.
• Use the dedicated virtual machine host's OCID as the search keyword.

After you have retrieved the log events for the dedicated virtual machine host, view the log event lower-level details, and check the contents of the responsePayload property. This property should contain the OCIDs for the instances that are running on the dedicated virtual machine host.

When designing your cloud footprint, we recommend that you plan to always launch the largest instance first. Here's why:

When you place instances on a dedicated virtual machine host, Oracle Cloud Infrastructure launches the instances in a manner to optimize performance. For example, a dedicated virtual machine host created based on the DVH.Standard2.52 shape has two sockets with 24 cores configured per socket. Instances are placed so that each instance will only use resources that are local to a single physical socket. In scenarios where you are creating and terminating instances with a mix of shapes, this can result in an inefficient distribution of resources, meaning that not all OCPUs on a dedicated virtual machine host are available to be used. It might appear that a dedicated virtual machine host has enough OCPUs to launch an additional instance, but the new instance will fail to launch because of the distribution of existing instances.

Continuing this example, say that you want to launch instances using a shape with 16 OCPUs. On a DVH.Standard2.52 dedicated virtual machine host, you can only launch a maximum of two instances with 16 OCPUs. You cannot launch a third instance with 16 OCPUs, even though the dedicated virtual machine host has 16 remaining OCPUs. You can, however, launch additional instances using shapes with a smaller number of OCPUs.

What this means is, when you're placing an instance on a dedicated virtual machine host, you can only create the instance if the host has sufficient capacity based on the shape of the instance. In the Console, you can only choose from the hosts with sufficient capacity. Similarly, when you place an instance on a dedicated virtual machine host using the API, CLI, or SDKs, the operation will succeed only if the dedicated virtual machine host has sufficient capacity.

If you have a dedicated virtual machine host that doesn't have enough capacity to launch instances, you can do any of the following things:

• Delete (terminate) instances you no longer need on the dedicated virtual machine host to make capacity available.
• Choose a different, smaller shape for the instance you are trying to place on the dedicated virtual machine host.
• Create a new dedicated virtual machine host to place the instance on.

For steps to manage dedicated virtual machine hosts, see the following topics.

• Creating a Dedicated Virtual Machine Host
• Deleting Dedicated Virtual Machine Hosts
• Listing Dedicated Virtual Machine Hosts
• Placing Instances on a Dedicated Virtual Machine Host
• Infrastructure Maintenance for Dedicated Virtual Machine Hosts