Product documentation
Create a Microsoft Azure catalog
View PDF

Write-back cache disk

September 6, 2025
Contributed by: 
C S

You can use the Azure temporary disk as write-back cache disk only if all the following conditions are satisfied:

  • The write-back cache disk must non-persist as the Azure temporary disk is not appropriate for persistent data.
  • The chosen Azure VM size must include a temporary disk.
  • The ephemeral OS disk is not required to be enabled.
  • Accept to place the write-back cache file on Azure temporary disk.
  • The Azure temporary disk size must be greater than the total size of (write-back cache disk size + reserved space for paging file + 1 GB buffer space).

Non-persistent write-back cache disk scenarios

The following table describes three different scenarios when a temporary disk is used for write-back cache while creating a non-persistent machine catalog.

Scenario Outcome
All conditions to use a temporary disk for write-back cache are satisfied. The WBC file mcsdif.vhdx is placed on the temporary disk.
Temporary disk has insufficient space for write-back cache usage. A VHD disk ‘MCSWCDisk’ is created and WBC file mcsdif.vhdx is placed on this disk.
Temporary disk has sufficient space for write-back cache usage but UseTempDiskForWBC is set to false. A VHD disk ‘MCSWCDisk’ is created and WBC file mcsdif.vhdx is placed on this disk.

Create a machine catalog with non-persistent write-back cache disk

To configure a catalog with non-persistent write-back cache disk, use the PowerShell parameter New-ProvScheme CustomProperties. The custom properties are:

  • UseTempDiskForWBC. This property indicates whether you are accepting to use the Azure temporary storage to store the write-back cache file. This must be configured to true when running New-ProvScheme if you want to use the temporary disk as write-back cache disk. If this property is not specified, the parameter is set to False by default.

For example, using the CustomProperties parameter to set UseTempDiskForWBC to true:

    -CustomProperties '<CustomProperties xmlns=" http://schemas.citrix.com/2014/xd/machinecreation" xmlns:xsi=" http://www.w3.org/2001/XMLSchema-instance"> `
    <Property xsi:type="StringProperty" Name="PersistWBC" Value="false"/> `
    <Property xsi:type="StringProperty" Name="PersistOsDisk" Value="false"/> `
    <Property xsi:type="StringProperty" Name="PersistVm" Value="false"/> `
    <Property xsi:type="StringProperty" Name="StorageAccountType" Value="Premium_LRS"/> `
    <Property xsi:type="StringProperty" Name="WBCDiskStorageType" Value="Premium_LRS"/> `
    <Property xsi:type="StringProperty" Name="LicenseType" Value="Windows_Client"/> `
    <Property xsi:type="StringProperty" Name="UseTempDiskForWBC" Value="true"/> `
    </CustomProperties>'
<!--NeedCopy-->

Note:

After you commit the machine catalog to use Azure local temporary storage for write-back cache file, it cannot be changed to use VHD later.

Create a machine catalog with persistent write-back cache disk

To configure a catalog with persistent write-back cache disk, use the PowerShell parameter New-ProvScheme CustomProperties.

Tip:

Use the PowerShell parameter New-ProvScheme CustomProperties only for cloud-based hosting connections. If you want to provision machines using a persistent write-back cache disk for an on-premises solution (for example, XenServer®) PowerShell is not needed because the disk persists automatically.

This parameter supports an extra property, PersistWBC, used to determine how the write-back cache disk persists for MCS provisioned machines. The PersistWBC property is only used when the UseWriteBackCache parameter is specified, and when the WriteBackCacheDiskSize parameter is set to indicate that a disk is created.

Note:

This behavior applies to both Azure and GCP where the default MCSIO write-back cache disk is deleted and re-created when power cycling. You can choose to persist the disk to avoid the deletion and recreation of MCSIO write-back cache disk.

Examples of properties found in the CustomProperties parameter before supporting PersistWBC include:

<CustomProperties xmlns="http://schemas.citrix.com/2014/xd/machinecreation" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Property xsi:type="StringProperty" Name="UseManagedDisks" Value="true" />
<Property xsi:type="StringProperty" Name="StorageAccountType" Value="Premium_LRS" />
<Property xsi:type="StringProperty" Name="ResourceGroups" Value="benvaldev5RG3" />
</CustomProperties>
<!--NeedCopy-->

Note:

This example only applies to Azure. The properties are different in the GCP environment.

When using these properties, consider that they contain default values if the properties are omitted from the CustomProperties parameter. The PersistWBC property has two possible values: true or false.

Setting the PersistWBC property to true does not delete the write-back cache disk when the Citrix DaaS™ administrator shuts down the machine from the management interface.

Setting the PersistWBC property to false deletes the write-back cache disk when the Citrix DaaS administrator shuts down the machine from the management interface.

Note:

If the PersistWBC property is omitted, the property defaults to false and the write-back cache is deleted when the machine is shut down from the management interface.

For example, using the CustomProperties parameter to set PersistWBC to true:

<CustomProperties xmlns="http://schemas.citrix.com/2014/xd/machinecreation" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Property xsi:type="StringProperty" Name="UseManagedDisks" Value="true" />
<Property xsi:type="StringProperty" Name="StorageAccountType" Value="Premium_LRS" />
<Property xsi:type="StringProperty" Name="ResourceGroups" Value="benvaldev5RG3" />
<Property xsi:type="StringProperty" Name="PersistWBC" Value="true" />
</CustomProperties>
<!--NeedCopy-->

Important:

The PersistWBC property can only be set using the New-ProvScheme PowerShell cmdlet. Attempting to alter the CustomProperties of a provisioning scheme after creation has no impact on the machine catalog and the persistence of the write-back cache disk when a machine is shut down.

For example, set New-ProvSchemeto use the write-back cache while setting the PersistWBC property to true:

New-ProvScheme
-CleanOnBoot
-CustomProperties "<CustomProperties xmlns=`"http://schemas.citrix.com/2014/xd/machinecreation`" xmlns:xsi=`"http://www.w3.org/2001/XMLSchema-instance`">
<Property xsi:type=`"StringProperty`" Name=`"UseManagedDisks`" Value=`"true`" />
<Property xsi:type=`"StringProperty`" Name=`"StorageAccountType`" Value=`"Premium_LRS`" />
<Property xsi:type=`"StringProperty`" Name=`"ResourceGroups`" Value=`"benvaldev5RG3`" />
<Property xsi:type=`"StringProperty`" Name=`"PersistWBC`" Value=`"true`" />
</CustomProperties>"
-HostingUnitName "adSubnetScale1"
-IdentityPoolName "BV-WBC1-CAT1"
-MasterImageVM "XDHyp:\HostingUnits\adSubnetScale1\image.folder\GoldImages.resourcegroup\W10MCSIO-01_OsDisk_1_a940e6f5bab349019d57ccef65d2c7e3.manageddisk"
-NetworkMapping @{"0"="XDHyp:\HostingUnits\adSubnetScale1\\virtualprivatecloud.folder\CloudScale02.resourcegroup\adVNET.virtualprivatecloud\adSubnetScale1.network"}
-ProvisioningSchemeName "BV-WBC1-CAT1"
-ServiceOffering "XDHyp:\HostingUnits\adSubnetScale1\serviceoffering.folder\Standard_D2s_v3.serviceoffering"
-UseWriteBackCache
-WriteBackCacheDiskSize 127
-WriteBackCacheMemorySize 256
<!--NeedCopy-->

Improve boot performance with MCSIO

You can improve boot performance for Azure and GCP managed disks when MCSIO is enabled. Use the PowerShell PersistOSDisk custom property in the New-ProvScheme command to configure this feature. Options associated with New-ProvScheme include:

<CustomProperties xmlns="http://schemas.citrix.com/2014/xd/machinecreation" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Property xsi:type="StringProperty" Name="UseManagedDisks" Value="true" />
<Property xsi:type="StringProperty" Name="StorageAccountType" Value="Premium_LRS" />
<Property xsi:type="StringProperty" Name="ResourceGroups" Value="benvaldev5RG3" />
<Property xsi:type="StringProperty" Name="PersistOsDisk" Value="true" />
</CustomProperties>
<!--NeedCopy-->

To enable this feature, set thePersistOSDisk custom property to true. For example:

New-ProvScheme
-CleanOnBoot
-CustomProperties "<CustomProperties xmlns=`"http://schemas.citrix.com/2014/xd/machinecreation`" xmlns:xsi=`"http://www.w3.org/2001/XMLSchema-instance`"><Property xsi:type=`"StringProperty`" Name=`"UseManagedDisks`" Value=`"true`" /><Property xsi:type=`"StringProperty`" Name=`"StorageAccountType`" Value=`"Premium_LRS`" /><Property xsi:type=`"StringProperty`" Name=`"ResourceGroups`" Value=`"benvaldev5RG3`" /><Property xsi:type=`"StringProperty`" Name=`"PersistOsDisk`" Value=`"true`" /></CustomProperties>"
-HostingUnitName "adSubnetScale1"
-IdentityPoolName "BV-WBC1-CAT1"
-MasterImageVM "XDHyp:\HostingUnits\adSubnetScale1\image.folder\GoldImages.resourcegroup\W10MCSIO-01_OsDisk_1_a940e6f5bab349019d57ccef65d2c7e3.manageddisk"
-NetworkMapping @{"0"="XDHyp:\HostingUnits\adSubnetScale1\\virtualprivatecloud.folder\CloudScale02.resourcegroup\adVNET.virtualprivatecloud\adSubnetScale1.network"}
-ProvisioningSchemeName "BV-WBC1-CAT1"
-ServiceOffering "XDHyp:\HostingUnits\adSubnetScale1\serviceoffering.folder\Standard_D2s_v3.serviceoffering"
-UseWriteBackCache
-WriteBackCacheDiskSize 127
-WriteBackCacheMemorySize 256
<!--NeedCopy-->
Write-back cache disk
September 6, 2025
Contributed by: 
C S
September 6, 2025
Contributed by: 
C S

In this article

Site feedback | Your privacy choices footer linkYour Privacy Choices | Privacy and legal terms | Cookie preferences | Consent settings | docs.cloud.com
© 1999- Cloud Software Group, Inc. All rights reserved.