Note: VMware Converter 5.0.1. is compatible with vSphere 5.1. See this updated blogpost on this issue.
After an (almost) succesful upgrade to vSphere 5.1, I had to convert a VMware Workstation virtual machine to VMware vSphere 5.1 using VMware Converter 5. After trying to connect to my freshly upgraded vCenter 5.1 server VMware Converter crashed with following error:
Exactly the same happens if you’re trying to connect directly to an ESXi 5.1 server.
Happily VMware published a KB article which addresses this issue. However, the solution…or workaround, is not too exiciting: Use an ESXi 5.0 host and connect this host to vCenter 5.1. Use the 5.0 host for the conversion and then migrate the virtual machine to an ESX 5.1 host for upgrading the virtual hardware etc.
This workaround will work, if you have not upgraded all your hosts or if have a spare host (and license) available. In my case all hosts are upgraded to 5.1, so I came up with the idea of the “VMware Converter Converter Virtual Appliance“…which is nothing more than a virtual machine that is running ESXi 5.0. Especially when you’re using iSCSI or NFS you can connect this host to your storage volumes very easily. Use the VMware Converter² Virtual Appliance as target server for VMware Converter and migrate virtual machines from this host to your 5.1 hosts.
If you don’t have any licenses available you can also run a stand alone instance of ESXi. After the conversion process to the ESXi 5.0 is complete, de-register the virtual machine and re-register the virtual machine on a 5.1 host (the storage should be shared between the hosts).
Although this trick will work, I hope VMware will publish a solution as soon as possible. The KB article tells: “VMware is working on a solution to ensure that Converter Standalone is compatible with the latest versions of vSphere. For information about new releases and updates, visit VMware vCenter Converter Standalone Product Download Center.”
More information on installing ESXi as a virtual machine is available here.
Update: It seems you can use VMware Converter 4.3 to convert to ESXi 5.1. More information in the KB article.