vMotion

vMotion is a feature in VMware's vSphere that enables the live migration of a running virtual machine from one ESXi host to another with minimal downtime. During the migration, the VM continues to run, and its memory, CPU state, and network connections are transferred to the destination host, preserving service continuity.

The migration process begins by establishing a session between the source and destination hosts over a dedicated vMotion network. The memory pages are copied iteratively while the VM executes, with pages dirtied by running applications tracked and resent. When the delta becomes small, the VM is briefly suspended, its final memory state and device state are transferred, and the VM resumes on the destination host with its virtual NICs and network identity intact.

Requirements for vMotion include shared storage accessible by both hosts for the VM’s disk files, compatible CPU features or Enhanced vMotion Compatibility (EVC) to avoid instruction set conflicts, and a properly configured vMotion network (VMkernel NIC) with sufficient bandwidth and low latency. In typical deployments, the hosts are managed by the same vCenter Server; Cross-VC vMotion enables migration across vCenter instances in newer versions. Some configurations also support storage vMotion to move disk files without migrating the running VM, but standard vMotion relies on shared storage.

Security and performance considerations include ensuring network isolation for vMotion traffic, enabling encryption where supported, and planning capacity to avoid prolonged migrations. vMotion is a core component of high-availability, load-balancing, and dynamic resource management in modern virtualized data centers.