by VCPHelp on 19/01/09 at 7:31 pm
VMotion is VMware’s name for one of the most useful technologies you’ll find as an administrator or consultant. VMotion allows the transitioning of a running virtual machine between different physical hosts without any downtime. By allowing this, admins can claim unheard-of uptime on servers, provide exceptional service to customers, and most importantly of all, reduce the hassle and workload on themselves!
VMotion requires shared storage that can be accessed by all of the ESX hosts which will be expected to run a VM. When you do a hot migration between hosts using Virtual Center, the VM is placed into snapshot mode, the memory of the VM transferred to the new location, and then snapshot mode is removed thus allowing the new host to write to the virtual machine’s files.
This ability to move VMs which are executing is the basis for the DRS (Distributed Resource Scheduler) as VMs can be rearranged on different ESX hosts to meet various CPU and memory requirements.
In addition to truly shared storage, VMotion requires a gigabit network and VMware Virtual Center.