What is VMware vMotion?

vMotion is the movement of a virtual machine (VM) from one host to another. It is VMware technology and, in VMware terms, it means the moving of a VM from one ESX/ESXi host to another. This is also termed as live migration. Storage vMotion is a similar term that refers to the moving of a VM from one datastore to another. The key takeaway is that VMotion happens without service interruption.

Why vMotion?

vMotion is essential to:

  • Perform hardware maintenance without any scheduled downtime.
  • Migrate VMs from underperforming or failing hosts.
  • Free up hosts and resource pools for other VMs.


How does VMware vMotion work?

vMotion works by migrating the entire state of a VM from one ESX host to another, including memory, MAC address, and other components. To explain in simple terms, vMotion takes place in the following steps:

  • The entire state of a VM is encapsulated by a set of shared storage files. VMware Virtual Machine File System (VMFS) allows multiple installations of the ESX server to access the same VM files concurrently.
  • The active memory and precise execution state of the VM are quickly transferred, instantaneously switching the VM's running to the targetted ESX host. Once the entire memory and system state has been copied over to the target ESX server, the source VM stops, copies the bitmap to the target ESX server, and resumes the VM on the target ESX server.
  • The underlying servers virtualize the networks being used so that even after migration, the VM's network identity and network connections are preserved. vMotion manages the virtual MAC address as a part of this process. Once activated on the new host, vMotion pings and notifies the new physical location and virtual MAC address to the network router.


Benefits of vMotion

  • Time-saving:

    The entire process takes place over a few seconds, averting interruptions.

  • Zero downtime:

    It results in zero downtime as the vMotion preserves the execution state, the network identity, and the active network connections.

  • Interoperability:

    You can migrate across different OS, hardware, and storage types supported by VMware ESX.

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