Does vMotion Data Route via the vCenter Server?

[Rob_Hughes]

Hi

I need some assistance with resolving a query that I have.

We currently have a vCenter server that is managing some clusters as well as some standalone hosts with local (non-shared) storage. The standalone hosts are physically located on remote sites. Some sites have more than one of these standalone hosts. We have a requirement to move a guest VM from one standalone host to another standalone host on the same remote site.

As there is no shared storage the VM will need to be shut down before attempting the vMotion.

The VM in question has a 4TB thick provisioned VMDK that will be migrated between the physical hosts.

I think that when the vMotion is kicked off the data will be confined to the subnet that the two physical hosts are connected and therefore will utilise the bandwidth available via the local networking equipment and will not leave the physical site. My colleague on the other hand has suggested that the data will travel via the vCenter server. Obviously this would cause an issue with trying to move so much data and would effectively mean that this 4TB would leave the remote site, travel via the vCenter server, and then return to the remote site. Not only would this be very slow it could also have a negative impact on the bandwidth to and from the site.

So my question is who is correct? (Assuming one of us is!)

Thanks

[npadmani · Accepted solution]

when you initiate cold migration of a VM by selecting migrate both (host and storage) where your both the hosts are based at same site, it will happen with source and target esxi host, it's not going to travel all the way to your vCenter host.

if your environment is vSphere 5.1 or higher, use web client and you can move VM while it's powered on and residing in local storage of the host. This feature is called Cross-Host migration. only available using web client.

[Rob_Hughes]

Thanks for the reply.

I wasn't aware of the Cross-Host migration functionality using the Web Client. Can you confirm that when using Cross-Host migration that the traffic will still be contained within the physical site where the hosts are located?

[npadmani]

yes, during cross host migration also, data will flow between source and target ESXi host only..