NetApp Training Brain Dump: Disk LED's and Loops

Wanted to pass on a nifty trick I learned recently: when dealing with multiple loops on a system, an easy way to figure out which shelves are physically on which loop is to turn on the LED of the corresponding disk on the first shelf.  For example, let's say DS14's cabled MPHA with 4 loops of 1 shelf each.  If one controller has a shelf on loop 1a-2a, turn on disk 17 (disk) LED and 18 (second disk) LED on that loop.  If 4b-7c is another loop, maybe turn on disks 3 and 6.  Obviously, how you choose to identify is up to your own pattern.

e.g.: led_on 1a.17

I also learned something interesting: according to this NetApp engineer, if you use the command that turns on all the LED's in a loop, it will take over all the IO on the loop and make the shelves completely inaccessible.  Wild.