Expand volumes on Azure Stack HCI and Windows Server clusters

Applies to: Azure Stack HCI, versions 22H2 and 21H2; Windows Server 2022, Windows Server 2019

This article explains how to expand volumes on a cluster by using Windows Admin Center and PowerShell.


Not supported: resizing the underlying storage used by Storage Spaces Direct. If you are running Storage Spaces Direct in a virtualized storage environment, including in Azure, resizing or changing the characteristics of the storage devices used by the virtual machines isn't supported and will cause data to become inaccessible. Instead, follow the instructions in the Add servers or drives section to add additional capacity before expanding volumes.

Expand volumes using Windows Admin Center

  1. In Windows Admin Center, connect to a cluster, and then select Volumes from the Tools pane.

  2. On the Volumes page, select the Inventory tab, and then select the volume that you want to expand. On the volume detail page, the storage capacity for the volume is indicated.

    You can also open the volumes detail page directly from Dashboard. On the Dashboard, in the Alerts section, select the alert, which notifies you if a volume is running low on storage capacity, and then select Go To Volume.

  3. At the top of the volumes detail page, select Settings.

  4. Enter a new larger size in the right pane, and then select Save.

    On the volumes detail page, the larger storage capacity for the volume is indicated, and the alert on the Dashboard is cleared.

Expand volumes using PowerShell

Capacity in the storage pool

Before you expand a volume, make sure you have enough capacity in the storage pool to accommodate its new, larger footprint. For example, when expanding a three-way mirror volume from 1 TB to 2 TB, its footprint would grow from 3 TB to 6 TB. For the expansion to succeed, you would need at least (6 - 3) = 3 TB of available capacity in the storage pool.

Familiarity with volumes in Storage Spaces

In Storage Spaces Direct, every volume is comprised of several stacked objects: the cluster shared volume (CSV), which is a volume; the partition; the disk, which is a virtual disk; and one or more storage tiers (if applicable). To resize a volume, you will need to resize several of these objects.

Diagram shows the layers of a volume, including cluster shard volume, volume, partition, disk, virtual disk, and storage tiers.

To familiarize yourself with them, try running the Get- cmdlet with the corresponding noun in PowerShell.

For example:


To follow associations between objects in the stack, pipe one Get- cmdlet into the next.

For example, here's how to get from a virtual disk up to its associated volume:

Get-VirtualDisk <FriendlyName> | Get-Disk | Get-Partition | Get-Volume

Step 1 – Expand the virtual disk

The virtual disk may use storage tiers, or not, depending on how it was created.

To check, run the following cmdlet:

Get-VirtualDisk <FriendlyName> | Get-StorageTier

If the cmdlet returns nothing, the virtual disk doesn't use storage tiers.

No storage tiers

If the virtual disk has no storage tiers, you can expand it directly using the Resize-VirtualDisk cmdlet.

Provide the new size in the -Size parameter.

Get-VirtualDisk <FriendlyName> | Resize-VirtualDisk -Size <Size>

When you expand the VirtualDisk, the associated Disk follows automatically and is resized too.

Animated diagram shows the virtual disk of a volume becoming larger while the disk layer immediately above it automatically becomes larger as a result.

With storage tiers

If the virtual disk uses storage tiers, you can expand each tier separately using the Resize-StorageTier cmdlet.

Get the names of the storage tiers by following the associations from the virtual disk:

Get-VirtualDisk <FriendlyName> | Get-StorageTier | Select FriendlyName

Then, for each tier, provide the new size in the -Size parameter:

Get-StorageTier <FriendlyName> | Resize-StorageTier -Size <Size>


If your tiers are different physical media types (such as MediaType = SSD and MediaType = HDD) you need to ensure you have enough capacity of each media type in the storage pool to accommodate the new, larger footprint of each tier.

When you expand the StorageTier(s), the associated VirtualDisk and Disk follow automatically and are resized too.

Animated diagram shows first one then another storage tier becoming large while the virtual disk layer and disk layer above become larger as well.

Step 2 – Expand the partition

Next, expand the partition using the Resize-Partition cmdlet. The virtual disk is expected to have two partitions: the first is Reserved and should not be modified; the one you need to resize has PartitionNumber = 2 and Type = Basic.

Provide the new size in the -Size parameter. We recommend using the maximum supported size, as shown below:

# Choose virtual disk
$VirtualDisk = Get-VirtualDisk <FriendlyName>

# Get its partition
$Partition = $VirtualDisk | Get-Disk | Get-Partition | Where PartitionNumber -Eq 2

# Resize to its maximum supported size
$Partition | Resize-Partition -Size ($Partition | Get-PartitionSupportedSize).SizeMax

When you expand the Partition, the associated Volume and ClusterSharedVolume follow automatically and are resized too.

Animated diagram shows the virtual disk layer, at the bottom of the volume, growing larger with each of the layers above it growing larger as well.

That's it!


You can verify the volume has the new size by running the Get-Volume cmdlet.

Next steps

For step-by-step instructions on other essential storage management tasks, see: