Can anyone tell or describe vMotion procedure in VMware , what actually happened behind the scene when performing vMotion?

In simple ... VMotion enables the live migration of running virtual machines from one physical server to another with zero downtime, continuous service availability, and complete transaction integrity. It is transparent to users.

In vMotion the virtual machine is "moved" from one host to another, this name is property from VMware. Other hypervisors have similar technologies with different names.

What happens internally is that the working memory is copied (from one host to another) and when the process is almost finished there will be another small memory copy containing the small changes that happened during the vMotion.

The machine will not loose identity, network connection, etc. In a gigabit network will take just a few seconds.

Hope this helps!

Gustavo