mine current HP R class machine comes with scsi but not usb port. i am thinking it is possible to get a scsi to usb converter to help to connect usb-enabled devices such as usb-enabled dvd writer, usb-enabled portable hard disk. pls advise. thanks 
SCSI and USB do not work that way...
You may have more luck with scsi-over-ethernet, using another machine to host the disks.