Hello Again
After several days of test my friend came with a good idea wich is to test every separate vmdk on different datastore with enough free space to make sure it will let the creation of minimum double the size of the original vmdk of the primary vm ... after several hours of activating the FT it worked .
the resolution is to choose a datastore wich has a free space at least as the size of the vmdk .
i think that FT on Version 6.0 requires double space to create the secondary vmdk and after the creation is complete and FT enabled it will remain at the original size .
to be confirmed...
thanks to this article for the workaround or for the solution.
Secondary VM can't started if more than 4x 2 TB VMDKs are connected