In vSphere version 5.1 or later, you can enable the disk space reclamation feature for Horizon 7. Horizon 7 creates linked-clone virtual machines in an efficient disk format that allows ESXi hosts to reclaim unused disk space in the linked clones, reducing the total storage space required for linked clones.

As users interact with linked-clone desktops, the clones' OS disks grow and can eventually use almost as much disk space as full-clone desktops. Disk space reclamation reduces the size of the OS disks without requiring you to refresh or recompose the linked clones. Space can be reclaimed while the virtual machines are powered on and users are interacting with their remote desktops.

Disk space reclamation is especially useful for deployments that cannot take advantage of storage-saving strategies such as refresh on logoff. For example, knowledge workers who install user applications on dedicated remote desktops might lose their personal applications if the remote desktops were refreshed or recomposed. With disk space reclamation, Horizon 7 can maintain linked clones at close to the reduced size they start out with when they are first provisioned.

This feature has two components: space-efficient disk format and space reclamation operations.

In a vSphere version 5.1 or later, when a parent virtual machine is virtual hardware version 9 or later, Horizon 7 creates linked clones with space-efficient OS disks, whether or not space reclamation operations are enabled.

To enable space reclamation operations, you must use Horizon Console to enable space reclamation for vCenter Server and reclaim VM disk space for individual desktop pools. The space reclamation setting for vCenter Server gives you the option to disable this feature on all desktop pools that are managed by the vCenter Server instance. Disabling the feature for vCenter Server overrides the setting at the desktop pool level.

The following guidelines apply to the space reclamation feature:

  • It operates only on space-efficient OS disks in linked clones.
  • It does not affect Horizon Composer persistent disks.
  • It works only with vSphere version 5.1 or later on virtual machines that are virtual hardware version 9 or later.
  • It does not operate on full-clone desktops.
  • It operates on virtual machines with SCSI controllers. IDE controllers are not supported.

Native NFS snapshot technology (VAAI) is not supported in pools that contain virtual machines with space-efficient disks.


  • Verify that your vCenter Server and ESXi hosts, including all ESXi hosts in a cluster, are version 5.1 with ESXi 5.1 download patch ESXi510-201212001 or later.


  1. In Horizon Console, navigate to Settings > Servers.
  2. On the vCenter Server tab, click Add and complete the Add vCenter Server wizard pages that precede the Storage Settings page.
  3. On the Storage Settings page, select Reclaim VM Disk Space.
    This option is selected by default if you are performing a fresh installation of Horizon 7. You must select Reclaim VM Disk Space if you are upgrading to a later release of Horizon 7.

What to do next

On the Storage Settings page, configure Horizon Storage Accelerator.

To finish configuring disk space reclamation in Horizon 7, set up space reclamation for desktop pools.