Hi there!
This question relates to if the disk shelf will be added to an existing stack (formerly loop) of shelves. It is suggested that SATA disks should be on a different stack, as well as 3G/6G and a seperate stack is required for 12G SAS shelves.
If you're adding a new shelf of disks that is the same type of disks to your existing disks, and you have 9 or less of that type of disk shelf (3 for SSD) connected to each controller pair, you will not need a new stack.
For an exact answer for your scenario, you should contact your netapp or partner solutions architect/engineer, or our professional services coordinator who asked that question.
Hope this helps!