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Which network uses svMotion? |VMware Communities


Thanks for the screenshot. I see what you mean now.

 

So remember when I said that a “cold” migration (i.e. svMotion) in your setup – that is, a setup that uses IP-based storage – will move the data over the host management network by default? Well, if you create a new vmkernel, assign it an IP address, and then click that “Provisioning traffic” box, it will use that network for svMotion and not the management network.

 

[Side note: It’s a little silly for the management network settings to have a “Provisioning traffic” check box since, if no other vmkernel has “Provisioning traffic” checked, svMotion will use the management network regardless of whether you check that box or not. Pretty confusing!]

 

So in other words, all those check boxes in your screenshot are there to enable you to separate different kinds of traffic over different vmkernel networks. If you create a new vmkernel network and click the “Provisioning traffic” check box and nothing else then “cold” migrations – and only “cold” migrations – will use that network.

 

I’ll answer your bullet point questions directly:

 

vMotion traffic: if enabled, is used to move RAM between hosts in a Hot Migration (vMotion); if disabled, vMotion doesn’t work

Correct. Unlike with svMotion, the “vMotion traffic” box must be checked on at least one vmkernel network, otherwise vMotion won’t function and therefore “hot” migrations won’t work.

shared nothing vMotion: if the virtual machine disk is on local datastore, we need to vMotion+svMotion: RAM is moved on vMotion traffic network; while the disk is moved on Management Network

Correct by default. Create a separate vmkernel and click “Provisioning traffic” to move VM disk data on that network instead of the management network. (Or, if you already have a separate vMotion vmkernel, you could just check the “Provisioning traffic” box on that one, so that you’re running both “hot” and “cold” migrations across that network.)

If the Virtual Machine is powered off (cold migration) the vMotion traffic network is never used

Strictly speaking, that’s not accurate; it depends. Imo, it’s easier to think of it this way: with IP-based storage, a “cold” migration will use the management vmkernel network by default, as noted above, or some other network if you’ve clicked the “Provisioning traffic” box on it. In either case, that network might also be the vMotion network. It depends where you’ve clicked those “vMotion traffic” and “Provisioning traffic” boxes. In very simple setups, it’s common to have only a single vmkernel – the management network – and to check the “vMotion traffic” box on it. In that scenario, all traffic – “hot”, “cold”, management, VM – will run over that network.

if cold migrate between 2 hosts a poff vm and storage is shared between hosts: nothing to move between hosts: no network used

This is only correct if the hosts and shared storage are all VAAI-capable. If VAAI is not available and you’re using IP-based shared storage (e.g. NFS, iSCSI), a “cold” migration is going to involve the host pulling all of the VM’s disk data up from [source datastore] via the management network (by default) or whichever network has “Provisioning traffic” enabled, and then sending it back the same way to [destination datastore], even though both datastores live on the same storage device. (Yes, this is horribly inefficient!)

if cold migrate between 2 hosts a poff vm and vmdk is on local datastore:

—- if there is the Provisioning traffic enabled it is used to move vmdk between hosts

—- if the Provisioning traffic is not enabled, it is used the management network to move vmdk between hosts

Correct.

This is what I have understood…. but I don’t find any official/clear documentation about it

Honestly, I sympathize. The official documentation isn’t very clear on this stuff and, imo, VMware makes it more confusing by talking about “hot” and “cold” migrations. I find it much easier to focus on the technologies involved – i.e. vMotion and svMotion – what they’re for and how they specifically work. It makes a lot more sense to me that way.



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