So if you're running Redhat el5 and looking for that needle in the haystack of rescanning for new san luns, this is what worked for us.

#cd /sys/class/scsi_host
#ls -1
to get how many adapters you have, they should be numbered sequentially, host0 - host(x)
#for i in 0 1 2 3……(x)
#do
#echo "- - -" > /sys/class/scsi_host/host$i/scan
#done

All standard disclaimers apply, this is Linux we're talking about here.