vCenter Server 6.7U1 migration – maintenance mode required

I have a vSphere 6.7 cluster managed by a vCenter 6.7 server that we wish to move to a new vCenter server running 6.7U1. We are using both vSAN and vDS. All the live migration instructions I’ve found indicate that this should be pretty simple — create the new vCenter server, export and import the vDS settings, create the storage policy, run a command on the CLI for each host, then start moving the hosts themselves.

Unfortunately at this last step, it seems that there is no longer a way to add a host to a new vCenter server without putting it in maintenance mode. Of course, this is a big problem if you’re trying to migrate a running/production cluster without downtime.

I’ve already tried disconnecting and removing a host from inventory before moving it to the new cluster, and that also requires it to be put into maintenance mode. It appears that since U1 there is no longer a way to simply move hosts to a new vCenter instance without putting them in maintenance mode, effectively locking us into the existing vCenter instance unless we want to schedule downtime for our cluster.

I saw a forum post about this [here](https://communities.vmware.com/thread/589417) but it was never updated with a resolution. Does anyone have a workaround for this?

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  1. I just did this. Add the host to the data center directly then drag it to the cluster object. Going to cluster directly required maintenance mode for some reason.

    Edit – did this for approximately 20 hosts, and have another 50 planned. No issues, worked every time and all the VMs stayed running.

  2. Can you migrate guests off one host, put it into maintenance mode, move to the new vcenter, take out of maintenance mode and migrate guests back? I know it’s a faff, but probably less so than trying to schedule downtime.

    From reading that link it looks like it’s the vSAN that’s requiring the hosts to go into maintenance mode. I recently migrated all our hosts to vcenter 6.7u1 without any of them entering maintenance mode despite it warning me that it would.

  3. This is the type of situation for which the vCenter Standalone Converter is often used. You can employ it, running on Windows desktop, to basically copy a running VM to another ESXi host or vCenter Server to which you can connect and for which you have credentials.

    My suggestion is to cold migrate, via SCP, your VMs as much as possible, shutting them down and copying them individually. Use the Converter for any VMs that must be switched with virtually no down time.

    You should test any VMs you convert before putting them into production on their new host. So you’ll have to disable networking or take other measures to accomplish this.

    Why didn’t you just upgrade your vCenter Server in place? No downtime then.

  4. Question:

    When you try to move a host to a new vCenter, but not put it in a cluster at the destination, does it still necessitate putting it in maintenance mode? I know without vSAN and distributed switches it just tells you that the host is already being managed by xxxx vCenter and asks you to confirm the move.

    If this works for you, then you can get your hosts half-way into their new home by adding them to the new vCenter OUTSIDE of the cluster they’ll eventually be in. You will need to put them in maintenance mode to move each into the cluster.

  5. Also: you’re making a config change to your hosts, which may require a new ha agent to be deployed to your hosts. When making this kind of change you should always enter maintenance mode to make sure you don’t cause issues with any running workloads.

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