[OT] Mixing SCSI drives on a bus

I have a SCSI bus installed on a machine. Right now it has Seagate ST34371W and Quantum XP34361WD drives on the bus I would like to add a Seagate ST39175LW to the same bus. Does anyone know if this would cause any problems? Are there any rules that should be followed when mixing SCSI types on the same bus? Should I even be doing this? Thanks, Ahbaid.