There is a script you can use for this that comes with the O/S

/usr/bin/rescan-scsi-bus.sh

If that is missing you could try…

[ "$USER" != "root" ] && echo "You need to be root!" && exit 1
for i in `ls /sys/class/scsi_host`
do
   echo "- - -" > /sys/class/scsi_host/${i}/scan
done

…this will scan ALL adapters for new disks.

Check ls /dev/sd* output for your additional disks.