In Red Hat Enterprise Linux 5.4, a new script, rescan-scsi-bus.sh, has been added to sg3_utils package, a set of low-level SCSI utilities. It uses the capabilities of the Linux kernel to add and remove SCSI devices without the need to reboot the machine or reload a kernel module.
This script should be considered tech-preview
When performing operations to dynamically configure and unconfigure LUNs, it is strongly recommended that IO be quiesced. It has been observed that online storage re-configuration may cause device name changes. This should be checked before resuming I/O, to avoid data loss.
Consult your storage array vendor documentation for possible restrictions regarding these issues.