I can honestly never remember the correct files for doing a rescan of a SCSI bus so I figured I'd post this here. This isn't rocket science, but is here for quick reference. This is confirmed to work on RHEL 5/6, CentOS 5/6 and OEL 5/6:
ADD NEW SCSI DEVICE (i.e. new scsi disk)
# for f in /sys/class/scsi_host/host*; do echo "- - -" > $f/scan; done
DETECT CHANGES IN EXISTING SCSI DISK (i.e. growing a hard disk in VMWare)
# for f in /sys/block/sd*; do echo 1 > $f/device/rescan; done
SAFELY DELETE BLOCK DEVICE FROM SYSTEM
# echo 1 > /sys/block/DEVICE-NAME-HERE/device/delete