Time sync after migration

(Strahinja Kustudić) #1

When migrating a VM (regular one, not live) OpenNebula does the following:

  1. Pauses the VM by saving its current state
  2. Copies that VM with its saved state to a different host
  3. Resume the VM

The problem with this is that when the VM is resumed, the clock on the VM continues from where it left of. Having ntpd/chronyd running on a guest doesn’t help, because they have some max time diff value at which they don’t adjust the time. This is especially a problem for big VMs which can take an hour (or even more) to migrate.

How do you overcome time sync problems when migrating VMs?