When allocating disk space, provide only enough space for the operating system, applications, and additional content that users might install or generate. Usually this amount is smaller than the size of the disk that is included on a physical PC.

Because data center disk space usually costs more per gigabyte than desktop or laptop disk space in a traditional PC deployment, optimize the operating system image size. The following suggestions might help optimize image size:

  • Remove unnecessary files. For example, reduce the quotas on temporary internet files.
  • Turn off Windows services such as the indexer service, the defragmenter service, and restore points. For details, see the Windows Desktops and Applications in Horizon document.
  • Choose a virtual disk size that is sufficient to allow for future growth, but is not unrealistically large.
  • Use centralized file shares or App Volumes for user-generated content and user-installed applications.
  • Enable space reclamation for vCenter Server to automatically reclaim space used by stale or deleted data within a guest operating system.

The amount of storage space required must take into account the following files for each virtual desktop:

  • The ESXi suspend file is equivalent to the amount of RAM allocated to the virtual machine.
  • By default, the Windows page file is equivalent to 150 percent of RAM.
  • Log files can take up as much as 100MB for each virtual machine.
  • The virtual disk, or .vmdk file, must accommodate the operating system, applications, and future applications and software updates. The virtual disk must also accommodate local user data and user-installed applications if they are located on the virtual desktop rather than on file shares.

    If you use instant clones, the .vmdk files grow over time within a login session. Whenever a user logs out, the instant clone desktop is automatically deleted and a new instant clone is created and ready for the next user to log in. With this process, the desktop is effectively refreshed and returned to its original size.

You can also add 15 percent to this estimate to be sure that users do not run out of disk space.