Scan FC LUN's in RHEL/CentOS

1.First find out how many disks are visible in “fdisk -l” .

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

2.Find out how many host bus adapter configured in the Linux box.you can use “systool -fc_host -v” to verify available FC in the system.

# ls /sys/class/fc_host
host0  host1  

In this case,you need to scan host0 & host1 HBA.

3.If the system virtual memory is too low ,then do not proceed further.If you have enough free virtual memory,then you can proceed with below command to scan new LUNS.

# echo "1" > /sys/class/fc_host/host0/issue_lip
# echo "1" > /sys/class/fc_host/host1/issue_lip

Note: You need to monitor the “issue_lip” in /var/log/messages to determine when the scan will complete.This operation is an asynchronous operation.

4.Verify if the new LUN is visible or not by counting the available disks.

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

If any new LUNS added ,then you can see more count is more then before scanning the LUNS.

Source: http://www.unixarena.com/