vmotion migration

vmotion allows working processes in a virtual machine to continue throughout a migration.the entire state of the virtual machines is moved to the new ESX server even while the data storage remains in the same datastore

 

the state information includes the current memory content and all the information that defines and identifies the virtual machine the memory content includes transaction data and whateever bits of the operating system and applications are in memory the definition and identification information stored in the state includes all the data that maps to the virtual machine hardware elements such as bios,devices cpu mac addresses for  ethernet cars and so forth.

 

how vmotion works?

 

1.

initiate the vmotion migration using the vi client the source host is esx1 and the target host is esx2 both source and target host have access to the shared datastore holding vm's fils .

 

2.the virtual machine 's memory state is copied over the vmotion network from the source to the target host. while the virtual machine's memory is being copied users continu to access the virtual machine and potentially update pages in memory.a list of  modified pages in memory is kept in a memory bitmap on the source host.

 

3.after most of the vm's memory is copied  from the source to the target host, the VM is quiesced meaning the VM is taken to a state where no additional activity will occur on the VM .the quiesce time is the only time in the VMotion amount of time.During this quiesce period ,VMotion starts to transfer the VM to the target host.Only the VM device state and the memory bitmap containing the list of pages that have changed are transfered over during this time.

 

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