Proxmox VM Live Migration | Migrate VM to another host without Downtime

  1. Cluster Setup: Ensure that your Proxmox hosts are part of the same cluster. A Proxmox cluster consists of multiple Proxmox VE servers (nodes) combined to offer high availability and load balancing to virtual machines. Nodes in a cluster share resources such as storage and can migrate VMs between each other.
  2. Shared Storage: Live migration requires shared storage accessible by both the source and target hosts. This shared storage can be implemented using technologies like NFS, iSCSI, or Ceph. Shared storage allows the VM’s disk images and configuration files to be accessed by any node in the cluster.
  3. Migration Prerequisites: Before initiating a live migration, ensure that the target host has enough resources (CPU, memory, storage) to accommodate the migrating VM. Proxmox will check these prerequisites before allowing the migration to proceed.
  4. Initiating Migration: In the Proxmox web interface (or using the Proxmox command-line interface), select the VM you want to migrate and choose the “Migrate” option. Proxmox will guide you through the migration process.
  5. Migration Process:
    • Pre-Copy Phase: Proxmox starts by copying the memory pages of the VM from the source host to the target host. This is done iteratively, with the majority of memory pages copied in the initial phase.
    • Stopping Point: At a certain point during the migration, Proxmox determines a stopping point. This is the point at which the VM will be paused briefly to perform a final synchronization of memory pages and state information.
    • Pause and Synchronization: The VM is paused on the source host, and any remaining memory pages and state information are transferred to the target host. This pause is usually very brief, minimizing downtime.
    • Completion: Once the final synchronization is complete, the VM is resumed on the target host. From the perspective of the VM and its users, the migration is seamless, and the VM continues to run without interruption on the target host.
  6. Post-Migration: After the migration is complete, the VM is running on the target host. You can verify this in the Proxmox web interface or using the command-line tools. The source host frees up resources previously used by the migrated VM.
  7. High Availability (HA): In a Proxmox cluster with HA enabled, if a host fails, VMs running on that host can be automatically migrated to other hosts in the cluster, ensuring minimal downtime.

Overall, Proxmox VM live migration is a powerful feature that enables you to move virtual machines between hosts in a Proxmox cluster with minimal downtime, providing flexibility and high availability for your virtualized environment.