In vSphere 5.1 and later, you can enable the disk space reclamation feature for Horizon 7. Starting in vSphere 5.1, 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 5.1 or later environment, 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 Administrator 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 View Composer persistent disks.
  • It works only with vSphere 5.1 or later and only 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.

View Composer Array Integration (VCAI) is not supported in pools that contain virtual machines with space-efficient disks. VCAI uses vStorage APIs for Array Integration (VAAI) native NFS snapshot technology to clone virtual machines.


  • 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 Administrator, complete the Add vCenter Server wizard pages that precede the Storage Settings page.
    1. Select View Configuration > Servers.
    2. On the vCenter Servers tab, click Add.
    3. Complete the vCenter Server Information, View Composer Settings, and View Composer Domains pages.
  2. On the Storage Settings page, make sure that Enable space reclamation is selected.
    Space reclamation is selected by default if you are performing a fresh installation of Horizon 7 5.2 or later. You must select Enable space reclamation if you are upgrading to Horizon 7 5.2 or later from Horizon 7 5.1 or an earlier release.

What to do next

On the Storage Settings page, configure View Storage Accelerator.

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