How to scan newly added LUN using rescan-scsi-bus.sh ?

ENV : RHEL 5.4 and later

I suggest you NOT to scan the existing LUNs since I/O operations are still in use and if you scan them it will/may corrupt the file system. So, I always suggest you to scan the new added device or storage. Once you add it, HBA will detect the device and then you can scan this non-existent LUNs to the HBA. As an example you can execute the command like :

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#rescan-scsi-bus.sh --hosts=1 --luns=2
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Note : I assume that on host 1/or on HBA 1, lun 2 doesn't exist.

For more details please get help from :

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#rescan-scsi-bus.s --help

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Online_Storage_Reconfiguration_Guide/rescan-scsi-bus.html
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Try :)