Whenever the topic of instance migration comes up, it normally ends in a spirited conversation among my OpenStack peers for various reasons. So as a responsible adult, I will go on recording and say that instance migration is not perfect.
It has its flaws and can be quirky at best. Migration, whether live or not, does have a practical use case to your OpenStack cloud. Within OpenStack, you have the capability of migrating instances from one compute node to another. Some of the reasons you may do this is for maintenance purposes and/or to rebalance resource utilization across the cloud. Also, keep in mind that there are multiple ways to clear out a compute node for maintenance and we will cover that in more detail in Chapter 8, Setup Active-Active Regions.
Note
As mentioned earlier, the OpenStack Compute service (Nova) has the functionality to migrate instances in a traditional method and the ability to live-migrate an instance as well.
We will first examine the traditional...