12.5. Live migrating a virtual machine by using the web console

Prerequisites

• You have installed the RHEL 10 web console.

  For instructions, see Installing and enabling the web console.

• The web console VM plugin is installed on your system.
• Hypervisor: The source host and the destination host both use the KVM hypervisor.
• Hosts: The source and destination hosts are running.

• Open ports: Ensure the following ports are open on the destination host.

  • Port 22 is needed for connecting to the destination host by using SSH.
  • Port 16514 is needed for connecting to the destination host by using TLS.
  • Port 16509 is needed for connecting to the destination host by using TCP.
  • Ports 49152-49215 are needed by QEMU for transfering the memory and disk migration data.
• CPU: The VM must be compatible with the CPU features of the destination host. To ensure this is the case, see Verifying host CPU compatibility for virtual machine migration.

• Storage: The disk images of VMs that will be migrated are accessible to both the source host and the destination host. This is optional for offline migration, but required for migrating a running VM. To ensure storage accessibility for both hosts, one of the following must apply:

  • You are using storage area network (SAN) logical units (LUNs).
  • You are using a Ceph storage clusters.
  • You have created a disk image with the same format and size as the source VM disk and you will use the --copy-storage-all parameter when migrating the VM.
  • The disk image is located on a separate networked location. For instructions to set up such shared VM storage, see Sharing virtual machine disk images with other hosts.

• Network bandwidth: When migrating a running VM, your network bandwidth must be higher than the rate in which the VM generates dirty memory pages.

  To obtain the dirty page rate of your VM before you start the live migration, do the following on the command line:

  1. Monitor the rate of dirty page generation of the VM for a short period of time.

     # virsh domdirtyrate-calc vm-name 30

  2. After the monitoring finishes, obtain its results:

     # virsh domstats vm-name --dirtyrate
     Domain: 'vm-name'
       dirtyrate.calc_status=2
       dirtyrate.calc_start_time=200942
       dirtyrate.calc_period=30
       dirtyrate.megabytes_per_second=2

     In this example, the VM is generating 2 MB of dirty memory pages per second. Attempting to live-migrate such a VM on a network with a bandwidth of 2 MB/s or less will cause the live migration not to progress if you do not pause the VM or lower its workload.

     To ensure that the live migration finishes successfully, your network bandwidth should be significantly greater than the VM’s dirty page generation rate.

     注意

     The value of the calc_period option might differ based on the workload and dirty page rate. You can experiment with several calc_period values to determine the most suitable period that aligns with the dirty page rate in your environment.

• Bridge tap network specifics: When migrating an existing VM in a public bridge tap network, the source and destination hosts must be located on the same network. Otherwise, the VM network will not work after migration.

• Confirm whether the VM appears in the list of VMs available on the destination host.
• Start the migrated VM and observe if it boots up.