On the properties page of the OS disk, click Size + performance on the left menu.

Take a snapshot to make a backup of the disk.

Navigate to the properties page for the OS disk.

In the Azure portal, stop the VM whose OS disk you want to expand.

Delete the System Reserved volume and extend the Windows volumeĪssign a larger disk SKU to the OS disk in the Azure portal.

Create a new boot volume in the remaining unallocated space.

Extend the System Reserved volume into the unallocated space.

Assign a larger disk SKU to the OS disk in the Azure portal.

To fix this problem, you need to perform the following steps: The newly created System Reserved partition in this case is assigned to partition 2, whose placement will appear to block partition 1, the OS volume, from being extended into unallocated disk space. If Azure Disk Encryption is later applied to the OS disk, a new System Reserved partition must then be added to the disk to support BitLocker. This default arrangement, shown below, allows the C: drive to be extended into adjacent unallocated space as needed.Ĭustomers, however, may create VMs based on custom images that assign the Windows (C:) volume to partition 1 and that do not define a System Reserved partition. Normally, the System Reserved partition is assigned to partition 1, and the Windows volume is assigned to partition 2. This partition holds the Boot Manager code and the Boot Configuration Database, and it reserves space for the startup files required for BitLocker. The placement of the System Reserved partition appears to block the C drive from being extended into any unallocated space on the disk.ĭuring a default Windows installation, a System Reserved partition is created on Disk 0. A System Reserved partition also appears immediately to the right of the Windows partition. You see the Extend Volume… option grayed for the Windows (C:) partition in an Azure VM. It also describes a workaround that allows you extend the OS volume as needed.

This article describes a problem that prevents you from easily extending the OS volume on some Azure VMs that have been encrypted with Azure Disk Encryption (ADE).

Windows extend volume greyed out