Migration of virtual machines across different Clusters

[derruben1993]

Dear Community,

i have a question regarding the migration across different Clusters.

But first the setup:

We have 3 physical hosts formed to one HA-Cluster.

The physical hosts and the vCenter server are licensed with Essential Plus, because of performance issues we are thinking about buying two more servers.

The hosts are connected to a SAN via ISCSI.

The two new servers should also act as a HA-Cluster but they will be licensed with the standard version.

Now we need to migrate the virtual machines, which are running on the three old servers, to the new ones.

The new servers can be connected to the same LUNs.

How am i able to do that without powering the virtual machines off?

I am sorry for my bad english.

If you have any further question, don´t hesitate to ask them. I am grateful for any help!

[MKguy]

You can vMotion VMs across clusters or to hosts being no part of any cluster with no downtime just fine, as long as you fulfill all the usual vMotion requirements that apply between hosts inside a cluster as well.

This works completely out of the box and since 5.5 you don't even need shared storage anymore, though that certainly helps in reducing migration time.

Just make sure the CPUs are compatible (migration from older CPU generation to newer inside the same family i.e. AMD/Intel works fine), the hosts can communicate via their vMotion vmkernel interfaces and the destination VM network is available on both. 6.0 also allows cross-vCenter and cross-vSwitch vMotion:

Cross vCenter Server vMotion requirements in VMware vSphere 6.0 (2106952) | VMware KB

If you're building two vCenters then you can also temporarily disconnect hosts from one cluster/vCenter, add them to the new one, migrate machines to the new hosts, disconnect the host and connect it to the old one again.

[derruben1993]

Hello MKguy,

first many thanks for your answer.

In the article you linked is the following notice:

• The source and destination vCenter Server instances and ESXi hosts must be running version 6.0 or later.

Unfortunatly the old vCenter is in Version 5.5. I guess we have a problem there.

If you're building two vCenters then you can also temporarily disconnect hosts from one cluster/vCenter, add them to the new one, migrate machines to the new hosts, disconnect the host and connect it to the old one again.

So you mean there are no issues with the licenses? I mean if i understand you right, I could take a essential plus licensed hosts out of the existing cluster and add it to another vcenter which is licensed with standard?

Best regards

Ruben Seelmeyer

[MKguy]

So you mean there are no issues with the licenses? I mean if i understand you right, I could take a essential plus licensed hosts out of the existing cluster and add it to another vcenter which is licensed with standard?

Essentially, yes, that's entirely possible. What are your plans with licensing? For a HA cluster you need a vCenter license and licenses for the new hosts. So you could just buy another essentials plus kit or buy a separate vCenter standard + separate ESXi standard licenses (will be expensive).

In either case can install the new hosts, but keep them running with the default 60 day eval licenses at first, meanwhile attaching the real licenses to old hosts you disconnected from the old cluster. Then you migrate the VMs and once the old host is empty, you disconnect it and re-attach it to the old cluster, freeing the real license you temporarily attached once again for your new hosts.

To avoid having to buy new licenses you could consider simply replacing your current hosts with more powerful ones, typically ones with plenty of RAM.

[derruben1993]

Okay, that really sounds good.

I will go for the seperate vCenter standard + seperate ESXi licenses, even if they are expensive but they are more future-proof.

I´ll summarize the points as i understand it:

1. I create a Cluster with the 2 new hosts with the evaluation license for 60-days
2. I disconnect one of the old hosts and license it with the standard license
3. Then I  add it to the new one (so that I have 3 hosts in the new cluster)
4. I migrate the vms from the old host
5. I connect the old host to the old cluster again
6. Then I can license the new hosts with the standard license

Is that okay?

Best regards

Ruben

[MKguy]

Yes, that will work.

Just to clarify some of you points:

2. You enter the licenses in vCenter and just attach the license when you add the host to the new vCenter.

3. The host doesn't even need to be in the same cluster, it can be just a standalone host under the same vCenter. Ideally the old and new host should have access to the same Datastores as well unless you want to transfer all VM disk data over the network through enhanced shared-nothing vMotion introduced in 5.1.

4. Just be aware that, as I mentioned earlier, the usual vMotion constraints apply in terms of CPU compatibility, vMotion vmkernel and VM network etc.

[derruben1993]

Hello MKguy,

okay, thank you very much.

I guess with your help i am now able to manage the migration in my company.

Have a nice day!

Best regards

Ruben