linux scsiinfo fails to retun hard disk serial #

Hello gurus,

I am trying to run the scsiinfo utility to read the hard disk
serial number by giving the command 'scsiinfo -s /dev/sda'. The
command works fine if the SCSI controller is on board.

Its a redhat 8.0 based system.

But if I try the same thing on another board having external SCSI
controller mounted on the PCI slot, it fails to give me the hard disk
serial number.
It just displays blank serial # as " Serial Number ' ' "

How can i read the HD serial number in this case.

Thanks for your reply,

Hiren