What Is VM Live Migration and How Does It Avoid Downtime?

Live migration moves a running virtual machine from one physical host to another without shutting down its operating system, so applications and users see zero or near-zero downtime. Most major virtualization platforms support it, and production data centers rely on it wherever services have to keep running.

Updated September 2026 · Mr.PlanB

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Overview

Migrating a VM used to mean shutting it down, exporting it, importing it on another host, and starting it again. That works, but the service is interrupted. Live migration avoids the interruption by transferring the VM's memory state, configuration, and execution context while the VM is still running.

The process usually uses a pre-copy mechanism. The target host first creates a shadow VM to receive the source machine's memory. Memory pages are then copied from the source to the destination while the VM keeps running, and any pages that change during the transfer are tracked and sent again in further rounds. When only a few changes remain, the source VM is paused briefly, the last memory differences are transferred, storage access is switched to the destination host, and the VM continues running there. Network switches are then updated so traffic goes to the new host.

Live migration also helps with load balancing and hardware maintenance, since administrators can move workloads off overloaded or aging servers without affecting business operations. It may need specific licensing, shared storage, compatible CPUs, and correct network configuration, and live migration between different platforms is usually not supported.

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