Convert fixed to thin provisioned volumes on Azure Stack HCI

Applies to: Azure Stack HCI, version 22H2

This article describes how you can use Windows PowerShell to convert existing fixed provisioned volumes to thin provisioned volumes inline on your Azure Stack HCI cluster.

Fixed versus thin provisioning

Fixed provisioning allocates the full size of a volume from the storage pool at the time of creation. This method is inefficient as a portion of the storage pool's resources are depleted despite the volume being empty.

Converting from fixed to thin provisioned volumes returns any unused storage back to the pool for other volumes to leverage. As data is added or removed from the volume, the storage allocation will increase and decrease accordingly.

Use PowerShell to convert volumes

Use PowerShell to convert from fixed to thin provisioning as follows:

1. Run PowerShell as Administrator.

2. Check the volume's allocated size, size, and provisioning type.

   For a non-tiered volume, run the following command:

   Get-VirtualDisk -FriendlyName <volume_name> | FL AllocatedSize, Size, ProvisioningType
   

   Here is a sample output for the preceding command:

   PS C:\> New-Volume -FriendlyName NonTierVol -Size 5TB -ProvisioningType Fixed
   
   DriveLetter  FriendlyName  FileSystemType  DriveType  HealthStatus  OperationalStatus
   -----------  ------------  --------------  ---------  ------------  -----------------
                NonTierVol    CSVFS_ReFS      Fixed      Healthy       OK
   
   PS C:\> Get-VirtualDisk -FriendlyName NonTierVol | FL AllocatedSize, Size, ProvisioningType
   
   Allocated Size   : 5497558138880
   Size             : 5497558138880
   ProvisioningType : Fixed
   

   For a tiered volume, run the following command:

   Get-StorageTier -FriendlyName <volume_name*> | FL AllocatedSize, Size, ProvisioningType
   

   Here is a sample output for the preceding command:

   PS C:\> Get-StorageTier -FriendlyName TierVol* | FL AllocatedSize, Size, ProvisioningType
   
   AllocatedSize    : 80530636800
   Size             : 80530636800
   ProvisioningType : Fixed
   
   AllocatedSize    : 26843545600
   Size             : 26843545600
   ProvisioningType : Fixed
   

3. Convert the volume from fixed to thin provisioned as follows:

   For a non-tiered volume, run the following command:

    Set-VirtualDisk -FriendlyName <volume_name> -ProvisioningType Thin 
   

   For a tiered volume, run the following command:

    Get-StorageTier <volume_name*> | Set-StorageTier -ProvisioningType Thin
   

4. Remount the volume for the change to take effect. A remount is needed as Resilient File System (ReFS) only recognizes the provisioning type at mount time.

   For single-server clusters, complete the following steps. Workloads may experience minor interruptions, it is recommended to do this operation during maintenance hours.

   1. Get the cluster shared volume (CSV) name:

      Get-ClusterSharedVolume
      

   2. Next, take the volume offline:

      Stop-ClusterResource -Name <name>
      

      Here is a sample output for the preceding command:

      PS C:\> Stop-ClusterResource -Name "Cluster Virtual Disk (TierVol)"
      
      Name                           State   Node
      ----                           -----   ----
      Cluster Virtual Disk (TierVol) Offline NodeA
      

   3. Then bring the volume back online:

       Start-ClusterResource -Name <name>
      

   For two-node and larger clusters, do the following:

   1. Get the CSV name and node names:

       Get-ClusterSharedVolume
      

   2. Next, move the CSV to another node to remount the volume:

       Move-ClusterSharedVolume -Name <name> -Node <new_node>
      

      Here is a sample output for the preceding command:

      PS C:\> Get-ClusterSharedVolume
      
      Name                               State  Node
      ----                               -----  ----
      Cluster Virtual Disk (NonTierVol)  Online NodeA
      Cluster Virtual Disk (TierVol)     Online NodeB
      
      PS C:\> Move-ClusterSharedVolume -Name "Cluster Virtual Disk (TierVol)" -Node NodeA
      
      Name                           State         Node
      ----                           -----         ----
      Cluster Virtual Disk (TierVol) Online        NodeA
      
      

   3. Then move the CSV back to its original node:

       Move-ClusterSharedVolume -Name <name> -Node <original_node>
      

5. (Optional) Space reclamation after fixed to thin conversion occurs naturally over time. To speed up the process, run slab consolidation from the node that the volume resides using the following command:

   Get-Volume -FriendlyName <name> | Optimize-Volume -SlabConsolidate
   

   Note

   Slab consolidation runs with low priority by default. To complete slab consolidation faster but with a small impact to foreground I/O, run the above command with the -NormalPriority parameter.

6. Confirm that ProvisioningType is set to Thin and AllocatedSize is less than the volume size (Size):

   For a non-tiered volume, run the following command:

   Get-VirtualDisk -FriendlyName <volume_name> | FL AllocatedSize, Size, ProvisioningType
   

   For a tiered volume, run the following command:

    Get-StorageTier -FriendlyName <volume_name*> | FL AllocatedSize, Size, ProvisioningType
   

Next steps

Learn more about storage thin provisioning.