Livemigraatiot

Livemigraatiot, or live migrations, refer to the process of moving a running virtual machine or service from one physical host to another with minimal downtime. This capability is central to modern virtualization and cloud environments, enabling maintenance, load balancing, fault tolerance, and capacity planning without interrupting service.

During a live migration, the source and destination hosts coordinate to transfer the VM’s execution state, memory, CPU state, and I/O state, while preserving active network connections in many configurations. The goal is to complete the transfer with only a brief pause for the final switch of execution to the destination, ideally imperceptible to users.

Two common techniques are used. Pre-copy migrates memory pages from the source to the destination while the VM continues to run; pages that change (“dirty” pages) are copied again in subsequent rounds until the set of pages is small enough to finish with a short stop-and-switch. Post-copy starts the VM on the destination with only a portion of its memory, then fetches the remaining pages from the source on demand. Storage can be migrated separately (storage live migration) or together with memory state, depending on the platform and configuration.

Requirements and considerations include support for live migration on both hosts, compatible hardware features, and access to shared or migratable storage. Network configuration must allow seamless redirection, and there are trade-offs between downtime, bandwidth, and performance. Migration may fail due to network issues or resource constraints, in which case rollback or retries are used. Common platforms for live migration include KVM/QEMU, VMware vSphere, and Hyper-V, with container migrations sometimes handled via checkpoint/restore techniques such as CRIU.