VMware Instant Clone (VM Fork)

VMware Instant Clone is a feature within VMware's vSphere software that enables an administrator to rapidly clone a running virtual machine. This feature was originally introduced as a technology preview called Project Fargo at VMworld 2014.

VMware Instant Clone is also sometimes called VM Fork, because of the way the process works. Traditionally, when a server administrator creates a new virtual machine it must be booted up, configured and loaded with the required software. Rather than creating a new virtual machine from scratch, when administrators create a new VM using the Instant Clone feature, they rely on the framework already in place on an existing VM. This allows server administrators to create VMs much faster – less than a second in some cases. The VMware Instant Clone feature essentially creates a fork off the existing VM (known as the parent VM) to create one or more child VMs. These child VMs all share the same memory and storage of the parent VM. When a change is made to a child VM, the change is not made to the shared memory and storage of the parent VM, but is instead recorded in delta files that track these changes. In some ways, this approach can be compared to the delta files used in VM snapshots, which track changes but are not complete backups.

The VMware Instant Clone feature has many practical applications – including as a tool for test and development. For example, a child VM could be created as a platform to test a new application, and then deleted when testing was complete. The feature can be useful for load or stress testing an environment. Administrators can also use Instant Clone to rapidly deliver virtual desktop instances to users. The Instant Clone feature is also a key part of VMware's Project Bonneville technology preview, which allows for the rapid deployment of containers within VMs.

This was last updated in August 2015

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