http://privexioc67u24lsmssoeixnml2exr3les4pbtyqtmv3zvonvcc72jyd.onion/articles/suggested-switches-routers-colo
While for the depth, we need to take into account there needs to be padding between the rows, so that there's space to both plug in ethernet cables in the front of each switch, and the power cables in the back of each switch. 2" should be enough, so 4 + 2 = 6 inches depth per switch.