Since I migrated my VMWARE environment to vSphere 4.1 Virtual Center, I started getting a few errors when adding existing disks to virtual machines.
The error says:
Adding existing IDE disk is not supported at the moment. IDE disks cannot be hot added or there are no free available IDE controller slots.
I realized that disk are old disks that are on my environment since older versions of virtual center and VMDK descriptor file contains a legacyesx value instead of the lsilogic value of current ESX versions.
Seems this parameter is not compatible with vSphere 4.1 anymore.
So, you need to edit the VMDK description file and replace
ddb.adapterType = legacyESX
to
ddb.adapterType = lsilogic
After that the disk could be attached to the virtual machine without any problem.
Check VMWARE KB 1025883 for more details
