Found another useful thing on the web. This is the quick guide to rescan and configure newly added LUNS in Linux. 


To configure the newly added LUNS on RHEL:


# ls /sys/class/fc_host
 host0  host1  host2  host3

 fdisk -l 2>/dev/null | egrep '^Disk' | egrep -v 'dm-' | wc -l

 echo "1" > /sys/class/fc_host/host0/issue_lip

 echo "- - -" > /sys/class/scsi_host/host0/scan

 echo "1" > /sys/class/fc_host/host1/issue_lip

 echo "- - -" > /sys/class/scsi_host/host1/scan

 echo "1" > /sys/class/fc_host/host2/issue_lip

 echo "- - -" > /sys/class/scsi_host/host2/scan

 echo "1" > /sys/class/fc_host/host3/issue_lip

 echo "- - -" > /sys/class/scsi_host/host3/scan

 cat /proc/scsi/scsi | egrep -i 'Host:' | wc -l

 fdisk -l 2>/dev/null | egrep '^Disk' | egrep -v 'dm-' | wc -l

Alternatively, we can
run the re-scan-scsi script.

To scan new LUNs on Linux operating system which is using QLogic driver 

You need to find out driver proc file /proc/scsi/qlaXXX. 

For example on my system it is /proc/scsi/qla2300/0 

Once file is identified you need to type following command (login as the root
):
 
# echo "scsi-qlascan" > /proc/scsi/qla2300/0
 # cat /proc/scsi/qla2300/0

Now use the script rescan-scsi-bus.sh new LUN as a device. Run script as follows:
 
# ./rescan-scsi-bus.sh -l -w

The output of ls -l /sys/block/*/device should give you an idea about how each device is connected to the system.