Honestly I cannot believe that i have not put this one up on Fatmin before. I have to add new disks to RHEL servers all the time and can never remember I can never remember this procedure. I end up hitting up google all the time.
Anyway the command below causes a rescan of the scsi bus which is what you need to do for your server to detect a newly added disk. I find myself doing this on virtual machines all the time. Oh and for the love of all that is holy, please create your new disk a logical volume, and dont be lazy and just format the disk and stick a filesystem on it.
In this example I am using host0 as the target, however this may differ on your box.
echo “- – -” > /sys/class/scsi_host/host0/scan