Ephemeral OS Disk in limited preview

Posted on 4 October, 2018

Program Manager, Azure Compute

Today we are delighted to share the limited preview of Ephemeral OS Disk, a new virtual machine (VM) and virtual machine scale set (VMSS) feature that allows you to create an OS disk directly on the host node, providing local disk performance and faster VM/VMSS reimage time.

This offering is based on your feedback to provide a lower cost OS disk able to deliver higher performance for stateless applications that require consistent, low read/write latency to OS disk, as well as frequent reimage operations to reset the VM(s) to the original state. This includes workloads such as website applications, game server hosting services, VM pools, computation jobs and more. Ephemeral OS Disks also work well for workloads that are leveraging low-priority VM scale sets.

Key comparisons between Persistent OS disk and Ephemeral OS disk

  Persistent OS Disk Ephemeral OS Disk
Size limit for OS disk 2 TiB

Up to 30 GiB for preview

Up to VM cache size at general availability

VM sizes supported All DSv1, DSv2, DSv3, Esv2, Fs, FsV2, GS
Disk type support Managed and unmanaged OS disk Managed OS disk only
Region support All regions All regions excluding sovereign clouds
Specialized OS disk support Yes No
Data persistence OS disk data written to OS disk are stored in Azure Storage OS disk data is stored to local host machine and is not persisted to Azure Storage
Stop-deallocated state VMSS instances and VMs can be stop-deallocated and restarted from the stop-deallocated state VMSS instances and VMs cannot be stop-deallocated
OS disk resize Supported during VM creation and after VM is stop-deallocated Supported during VM creation only
Resizing to a new VM size OS disk data is preserved OS disk data is deleted, OS is re-provisioned

How to join preview

To enroll in the limited public preview, you will need to submit this form and your subscription will be approved within 24 to 48 hours starting October 10, 2018. You can check the status of your request by running the following PowerShell command:


Get-AzureRmProviderFeature -FeatureName localdiffdiskpreview -ProviderNamespace Microsoft.Compute

CLI 2.0:

az feature show --namespace microsoft.compute --name localdiffdiskpreview

We would love to get your feedback via Microsoft Teams or email EphemeralOSDiskvTeam@microsoft.com.