This morning I rebooted the ESX host after disabling hyperthreading. The server came back online but I can't connect to it via the VI console anymore. Has anyone an idea how to solve this?
What is the error message you're getting?
Can you ssh to the server?
if so try to restart a few services.
\# service vmware-vmkauthd restart
\# service xinetd restart
\# service mgmt-vmware restart
This shouldn't impact running of the machines. What service you actually need to restart depend on the error message. You can do all 3. If you still can't connect you might want to verify your network settings.
\# netstat -netlp
You may find that some networking process is defunct. See if you can kill-9 that process.
Check as well xinetd if it seem to have a higher pid now that before you restarted it.
vmkauthd, try to restart that one again, check this time to make sure it doesn't just say "already running" verify that the pid has changed afterwards.
After more than 5 hours I finally can reconnect to the hosts via the console although I didn't change anything. The virtual servers are back online. Some of these still crash to a blank console screen after a while. This was the reason why i rebooted the hosts in the first place.