vMotion background

[JaiKishan]

Hi,

When we do a Hot vMotion, what exactly happens at the background. What files is created, what file is moved from where to where, what file is deleted if any applicable?

Thanks,

jK

[Troy_Clavell]

a vMotion at a high level ,is a tranfer of the memory state of a guest from one ESX(i) to the other.

[JaiKishan]

Hi Troy,

What exactly do you mean by the memory state, is the memory state stored in a file?

If yes, which file is created and where that file is located.

From where to where the file is moved.

If no, how the memory state and cpu state is moved, what is the exact background process?

Thanks,

jK

[a_p_]

There is vMotion which - like Troy already mentioned - moves the memory to another host and there is Storage vMotion which leaves the VM running on the same host, but moves the virtual disks to another storage.

see http://www.vmware.com/products/vmotion/ and http://www.vmware.com/products/storage-vmotion/

André

[JaiKishan]

Hi Andre,

What exactly do you mean by the memory state, is the memory state stored in a file?

If yes, which file is created and where that file is located.

From where to where the file is moved.

If no, how the memory state and cpu state is moved, what is the exact background process?

Thanks,

jK

[Troy_Clavell]

maybe this will help

http://www.vmware.com/files/pdf/VMware-VMotion-DS-EN.pdf

[a_p_]

In a nutshell:

For vMotion you need shared storage - visible to all hosts - on which the VM's files (virtual disks, configuration files, ...) are located. On each host you have to setup a vmkernel port for vMotion on a network, visible for the other host's vMotion vmkernel port. Since all hosts are able to see the files, there's no need to transfer any files from host-A to host-B during vMotion, only the memory in use by the VM on host-A has to be transferred to the host-B. Once the memory is synchronized, host-A pauses the VM and releases any file locks on the datastore. Then host-B locks the files, takes over the workload and resumes the VM.

André

[JaiKishan]

Hi Andre,

Yes I very much understood the process, but when u say "only the memory in use by the VM on host-A has to be transferred to the host-B" where is this memory stored, is it a file which stores the content, and what about the LIVE data being dumped into the VM while it is running, where is this info stored?

Thanks,

J

[a_p_]

It's the real memory, currently in the host's RAM (DIMMs) which is transferred to the other host's RAM.

vMotion uses intelligent techniques to synchronizes the live contents of the RAM.

Take a look at "How does vMotion work" at the link Troy Clavell provided in his previous post.

André

[Sundararajan]

1. Shadow VM created on the destination host.

2. Copy each memory page from the source to the destination via the vMotion network. This is known as preCopy.

3. Perform another pass over the VM’s memory, copying any pages that changed during the last preCopy iteration.

4. Stun the VM on the source and resume it on the destination.

[amariamcool]

How vmotion Background Process run just go through this link you get an idea

VMOTION BACKGROUND PROCESS | VMware Interview Questions

and also Vmware Vsphere Related Interview Questions go through this link

VMware Interview Questions |