Some time ago I had some problems with a new configuration of VMotion. As soon as I started a VMotion of a running virtual machine, the process stopped at 10% and returned an 'Invalid fault' error:

 I knew I've seen such an error a long time ago, when I did my first VMware HA setups in 2004 but I quite couldn't remember the exact cause of it. This summarized task list helped me to remember it.

The simple cause is that the ESX hosts must resolve the DNS shortnames using the /etc/hosts file. So if you run into trouble, you have to add the server's short names into /etc/hosts like this:

127.0.0.1       localhost
::1             localhost
10.1.2.141   ESX01
10.1.2.142   esx02.localdomain.net esx02
10.1.2.143   esx03.localdomain.net esx03
10.1.2.144   esx04.localdomain.net esx04
10.1.2.145   esx05.localdomain.net esx05
10.1.2.146   esx06.localdomain.net esx06
10.1.2.147   esxi1.localdomain.net esxi1
10.1.2.148   esxi2.localdomain.net esxi2
10.1.2.149   esxi3.localdomain.net esxi3

After this, vmotion was working fine!