Now in public preview: Ephemeral OS disk support on Azure Virtual Desktop

Microsoft

Oct 15, 2025

Azure Virtual Desktop continues to evolve with features that simplify deployment and management of session hosts for our customers. Today, we’re excited to announce the public preview of Ephemeral OS disk support, the latest milestone in our Enhanced Host Pool Management initiative. Designed for stateless workloads, Ephemeral OS disk stores the operating system on the virtual machine’s local storage, rather than remote storage. This enables a faster session host creation experience and improved performance, while maintaining a consistent and responsive user experience.

Key benefits

Ephemeral OS disk offers:

Faster provisioning and reimaging: Session hosts can be created or reset.

Improved Performance: By keeping read/write operations local, users experience faster access times and reduced latency.
Optimized for stateless workloads: Ideal for environments that do not need to retain session host state information between uses.

What is Ephemeral OS disk?

Ephemeral OS disk stores the operating system on the virtual machine’s local storage, within the same physical server where the VM runs. This design eliminates the need to connect to remote Azure Storage, helping reduce network latency and deliver faster disk performance (IOPS).

Virtual machines that use ephemeral OS disks operate a bit differently. They can’t be started or deallocated. Instead, they can only be reimaged or deleted. This ensures each session host begins or is reset to a clean, consistent state, reducing management overhead and simplifying operations for environments that require frequent refresh cycles.

Because the disk is local and non-persistent, any changes made during a session are lost when the VM is reimaged or deleted. As a result, ephemeral OS disks are an excellent fit for stateless workloads that value speed, scalability, and rapid reimaging over long-term data retention.

Getting Started

To use ephemeral OS disks, a pooled host pool with a session host configuration (public preview) enabled is required. Ephemeral OS disks are not available for personal host pools or for host pools without a session host configuration.

You can configure a session host with Ephemeral OS disk for your pooled host pools using Azure Portal.

To configure a session host with an Ephemeral OS disk

From the Azure Portal, on the Azure Virtual Desktop blade create a new pooled host pool configured with a session host configuration.
On the session host tab:
- Select an image of your choice.
- Choose a VM size that has enough local disk space (either cache or temporary storage) to support your OS image. To find which VM sizes are compatible with your selected image, refer to the PowerShell script mentioned in the FAQ under the question: “Will all VM sizes be supported for ephemeral OS disks?”.
- Check the Ephemeral OS disk box.
- Select disk placement based on your VM type:
  - OS cache
  - Temp disk
Complete the remaining fields to create your host pool and session host.

Using Dynamic Autoscaling plans with Ephemeral OS Disks

Ephemeral OS disks are designed for stateless workloads and don’t support traditional start or deallocate operations. To ensure reliable scaling and lifecycle management, we recommend using Dynamic Autoscaling plans when deploying session hosts with ephemeral OS disks.

With this setup, session hosts are created and deleted according to the rules defined in your scaling plan, ensuring efficient resource use while aligning with the stateless design of ephemeral OS disks.

Learn more about Dynamic Autoscaling plans.

Next steps

We’re excited for you to begin exploring Ephemeral OS disk on Azure Virtual Desktop. We encourage you to check out our documents that include setup guidance, prerequisites, and much more to help you get started.

Want to learn more?