VMware vMotion Process

VMware VMotion moves live, running virtual machines from one host to another while maintaining continuous service availability. 

vMotion allows you to:

• Perform live migrations with zero downtime, undetectable to the user.
• Continuously and automatically optimize virtual machines within resource pools.
• Perform hardware maintenance without scheduling downtime and disrupting business operations.
• Proactively move virtual machines away from failing or under-performing servers.

    

How Does VMware VMotion Work?

Live migration of a virtual machine from one physical server to another with VMware VMotion is enabled by three fundamental technologies.

First, the entire state of a virtual machine is encapsulated by a set of files stored on shared storage such as Fibre Channel or iSCSI Storage Area Network (SAN) or Network Attached Storage (NAS). VMware vStorage VMFS allows multiple installations of VMware ESX® to access the same virtual machine files concurrently.

Second, the active memory and exact execution state of the virtual machine is rapidly transferred over a high speed network, allowing the virtual machine to immediately switch from running on the source ESX host to the destination ESX host. VMotion keeps the transfer period invisible to users by keeping track of on-going memory transactions in a bitmap. Once the entire memory and system state has been copied over to the target ESX host, VMotion suspends the source virtual machine, copies the bitmap to the target ESX host, and resumes the virtual machine on the target ESX host. This entire process takes less than two seconds on a Gigabit Ethernet network.

Third, the networks being used by the virtual machine are also virtualized by the underlying ESX host, ensuring that even after the migration, the virtual machine network identity and network connections are preserved. VMotion manages the virtual MAC address as part of the process. Once the destination machine is activated, VMotion pings the network router to ensure that it is aware of the new physical location of the virtual MAC address. Since the migration of a virtual machine with VMotion preserves the precise execution state, the network identity, and the active network connections, the result is zero downtime and no disruption to users.

 

Moving the VM from one esx to another ESX

Choose the VM -> rclick -> Migrate 

Chose the migration type 
  host/ datastore / Both host and data store
 Note: Change both host and data store option will be avail only when the VM is powered off. If you want to migrate both the host and datastore to some other datacenter or some where you need to power off the VM and select the "change both host and data store" option proceed as usual.

 Select the destination where you want to move your VM.

1.High Priority: reserve cpu for optimal vmotion performance [recommended] – if sufficient cpu resources are not immediately available , vmotion will not be initiated

2.Standard Priority: perform with available cpu resources if lack of cpu resources, the duration of vmotion may be extended

VMotion uses the Port no 8000 as default

VMotion fails:

1. Check the ports 8000 is open or not 
2. Ensure VMKerenl Port, VMotion Option is enabled

3. Vmkping <vmkernel IP>

4. telnet 8000 
5.Open console -> vpxa agent is running or not ( grep vpxa)

6. Ensure CD-ROM is not mounted.
7. Ensure VM Direct path is disabled.