Thanks for responding; however that document is supplied with my system & doesn't reference the scenaio.
FAS2552 connecting to multiple DS4246 shelves
FAS2552 connecting to multiple DS2246 shelves
My scenario is a FAS2552 with 2 x DS2246 shelves (matching option-2 above), to which I need to add a DS4246 shelf. This is where the problem begins. The DS2246 are dual controller, so the cabling logic is clear, but the DS4246 is single controller & it is not obvious how to insert this into the loop (& essentially where).
The DS4246 definitely has 2 IOMs. There is one on top and one on bottom. It does look a little weird since the 2246 has the IOMS side-by-side. Treat the top one like you would the left one and the bottom like the right.