For disks connected using Fibre Channel-Arbitrated Loop (FC-AL or FC), the loop ID is an integer between 16 and 126. The loop ID identifies the disk within its loop, and is included in the disk name, which identifies the disk uniquely for the entire system.
The loop ID corresponds to the storage shelf number and the bay in which the disk is installed. The lowest loop ID is always in the far right bay of the first storage shelf. The next higher loop ID is in the next bay to the left, and so on. You can view the device map for your storage shelves by using the fcadmin device_map command, available through the nodeshell.
For more information about the loop ID map for your storage shelf, see the hardware guide for the storage shelf.