I have a possible solution to this but wondering if anyone had a better idea?
I have a vCenter server which is a virtual machine hosted on a VMware 5.0 U3 platform (4 Host HA cluster). The SCSI controller for this server is an 'LSI Logic SAS' and I would like to change this to 'Paravirtual'.
Now the procedure for this is to add a 1MB (VM best practice says 1GB why?) disk on a different iscsi bus using the paravirtual SCSI controller, then shutdown the VM, remove 1MB disk and change the original SCSI controller type to Paravirtual. Simples Right?
Ok, so you add you 1MB disk on a paravirtual SCSI controller and shutdown the VM but wait a minute... its running you vcentre! DOH! now you cant make any changes and your vcentre is down... mmmm. OK log into the host running the vCenter server and make the changes there right? wrong! The host is being controlled by the vcentre server and VMware gives you a lovely error message that "resources for this virtual machine can only be done from <Ip_address of vcentre server you just shut down>.... How infuriating! At least you can power-on you vCenter server I guess 
So your vCenter server is now backup at least and you just spent ten minutes and caused a brief outage to you vCenter server with no result.
The only way I can get arround this is by creating a clone of my vCenter server and during the process use the 'Edit Hardware Settings' Experimental to change the SCSI controller. But really?
Can anyone else help me think around this issue?
All help greatly appreciated 
ALF4