An automated instant-clone farm consists of Linux hosts that are instant-clone virtual machines in vCenter Server.

Overview of Instant-clone Farms

An automated instant-clone farm is created from a golden image using the vmFork technology (called instant clone API) in vCenter Server. In addition to using the instant clone API from vCenter Server, VMware Horizon 8 creates several types of internal VMs (Internal Template, Replica VM, and ParentVM) to manage these clones in a more scalable way.

Horizon Connection Server creates instant-clone virtual machines based on the parameters that you specify when you create the farm. Instant clones share the virtual disk and memory of an internal parentVM, which contributes to reduced storage requirements and fast provisioning. Once the instant-clone VM is provisioned and the machine starts to be used, additional memory is utilized.

Although helpful in speeding up the provisioning speed, the use of parentVM does increase the memory requirement across the cluster. Sometimes when the benefit of having more memory outweighs the increase in provisioning speed, Horizon 8 automatically chooses to provision instant clones directly from replicaVM, without creating any parentVM. This feature is called Smart Provisioning. A single instant clone farm can have both instant clones that are created with parentVMs or without parentVMs.

An instant-clone desktop farm has the following benefits:
  • The provisioning of instant clones is fast, with or without using parentVM.
  • Instant clones are always created in a powered-on state, ready for use.
  • You can patch a farm of instant clones in a rolling process with zero downtime.

Workflow of Creating Instant Clones

Publishing an image is a process by which internal VMs needed for instant cloning are created from a golden image and its snapshot. This process only happens once per image and might take some time.

Horizon 8 performs the following steps to create a pool of instant clones:

  1. Horizon 8 publishes the image that you select. In vCenter Server, four folders (ClonePrepInternalTemplateFolder, ClonePrepParentVmFolder, ClonePrepReplicaVmFolder, and ClonePrepResyncVmFolder) are created if they do not exist, and some internal VMs that are required for cloning are created. In Horizon Console, you can see the progress of this operation on the Summary tab of the desktop pool. During publishing, the Pending Image pane shows the name and state of the image.
    Note: Do not tamper with the four folders or the internal VMs that they contain. Otherwise, errors might occur. The internal VMs are removed when they are no longer needed. Normally the VMs are removed within 5 minutes of pool deletion or a push-image operation. However, sometimes the removal can take up to 30 minutes. If there are no internal VMs in all four folders, these folders are unprotected and you can delete these folders.
  2. After the image is published, Horizon 8 creates the instant clones. This process is fast. During this process, the Current Image pane in Horizon Console shows the name and state of the image.

After the farm is created, you can change the image through the push-image operation. As with the creation of a farm, the new image is first published. Then the clones are recreated.

When an instant-clone pool farm is created, Horizon Console spreads the pool across datastores automatically in a balanced way. If you edit a farm to add or remove datastores, rebalancing of the cloned VMs happens automatically when a new clone is created.