XenServer 6.2 introduced Clone on Boot
This feature supports Machine Creation Services (MCS) which is shipped as part of XenDesktop. Clone on boot allows rapid deployment of hundreds of transient desktop images from a single source, with the images being automatically destroyed and their disk space freed on exit.

General cloning capabilities: When cloning VMs based off a single VHD template, each child VM forms a chain where new changes are written to the new VM, and old blocks are directly read from the parent template. When this is done with a file based vhd (NFS) then the clone is thin provisioned. Chains up to a depth of 30 are supported but beware performance implications.

Comment: Citrixs desktop virtualization solution (XenDesktop) provides two additional technologies that use image sharing approaches:
- Provisioning Services (PVS) provides a (network) streaming technology that allows images to be provisioned from a single shared-disk image. Details: http://bit.ly/2d0FrQp
- With Machine Creation Services (MCS) all desktops in a catalog will be created off a Master Image. When creating the catalog you select the Master and choose if you want to deploy a pooled or dedicated desktop catalog from this image.
Note that neither PVS (for virtual machines) or MCS are included in the base XenServer license.