vmkfstools -i/vmfs/volumes/EVAStorage2/PRTG_NM/PRTG_vmdk -d thin /vmfs/volumes/SAN-Fata-Storage/PRTG_NM/PRTG_NM.vmdk
If this is the exact command you used, then there are 2 typos in it. A missing space behind the "-i" and and "PRTG_vmdk" instead of "PRTG.vmdk" as the source disk. Btw. what type of storage do you use (NFS, iSCSI, FC)?
André