How to best move a media item from one server to another without too much of interruption for the user? This video shows two models of Virtual Machine live migration.
In case 1, we are using standard pre-copy migration: When all pages have been transferred from one server to another, the virtual machine is resumed and the video continues playing. However, because the clock is updated when the VM is resumed, it skips ahead in the video.
In case 2 we are using pre-copy migration with XBZRLE compression, i.e. we send changes to pages between iterations instead of full pages. This time, the virtual machine is only suspended for a short time (less than 0.5 s) before it is resuming.
In ORBIT, we are not going to use this method, instead we are going to use post-copy.
In post-copy migration, every memory page is transferred once and once only. Which means that post-copy is even better than using compression and only causes a minimum amount of suspension. A demonstration of this can be seen in the video below:
The next video below shows a demonstration of a post-copy migration with a modified OpenStack, which now supports the new LibVirt features for post-copy live migration. As the video shows, in OpenStack users can now choose either normal (pre-copy) migration or post-copy migration, which in turn calls LibVirt with the appropriate flags to perform the migration with the desired technique.
OpenStack is an open source software for cloud computing, especially for virtualisation and storage management. LibVirt is an open source API and management tool for managing platform virtualization.



