VMWare VM Migration 5.1 to 6.5


New Member
Mar 8, 2018
Hello Gang,

I'm implementing a new ESXi infrastructure at work, and I'm running into a little bit of a quandary with migrating VMs between different environments. I'll give you an overview of the environment to make this question easier to follow.

Current Infrastructure:
- 3 ESXi 5.1 hosts in a cluster, managed by a vCenter Server running 5.5 with vSphere Essentials License. (Dell R710s)
-Dell MD3600i SAN
-iSCSI Switches are Dell Force10
-Core Switch(s) are 3750Xs in a Stack

New Infrastructure:
-3x ESXi 6.5 Hosts in a Cluster, Managed by a vCenter Server also running 6.5 with vSphere Essentials License (Cisco UCS C220 M5s)
-Netapp FAS2650 SAN
-Pair of Nexus 3524Xs for backbone and iSCSI
-10GB thoughout and up-linked to 3750X Stack

The question to you VMWare folks is, what is the best approach to migrating VMs from the 5.1 environment to the 6.5 environment? I'd like to have minimal downtime if possible and avoid cold migrations. Here are some scenarios I have found around the Internet and on other forums.

#1 Have 2 vCenter Servers running at 6.5, upgrade 5.1 hosts to 6.5 and use the VMWare "Connector" to migrate between both environments

#2. Get a trial key for ESXi 6.5, remove 1 old host and introduce a new host and migrate VMs. Repeat for other 2 hosts.

#3 Use Veeam To Replicate VMs to the new infrastructure.


New Member
Oct 11, 2017
Good afternoon. I recently migrated 6 HP BL660c Hosts running esx/vcenter 6.0, to 12 Cisco UCS B200 M5's running esx/vcenter 6.5.

The approach I took was doing a cross vcenter vmotion. I'm not sure if it is available on the essentials license. You can migrate the machines hot. Here is a good matrix on version compatibility.
Cross vCenter Server operations (clone / migrate) between versions of vSphere 6.x

I had to use PowerCLI script since my vCenters did not match. We tried to upgrade vCenter first so they would match, but kept getting errors and gave up since it was going away anyhow. I based my script off of one like this:
vMotion between two vCenter Servers with different SSO domains - IVOBEERENS.nl

One easy way to migrate machines, which is independent of versions:
1. Power off VM on old host.
2. unregister VM on old host.
3. Go to new host and register VM and point to the virtual machine.vmx file.
4. Power on VM and your ready to go. On initial power on you may need to select network if it's not an exact match.
VMware Knowledge Base

We used a trial key which is valid for either 30-60 days. After everything was migrated over I moved the licenses over.

I did try Veeam as a test, but it was slow compared to PowerCLI script.