That's not the point. 9s and SLAs are contractural obligations, not laws of physics that cannot be broken. I saw many systems engineered for a lot of 9s be dow

That's not the point. 9s and SLAs are contractural obligations, not laws of physics that cannot be broken. I saw many systems engineered for a lot of 9s be down hard for much longer than 9s promised, most often due to perfect storm of issues. 9s are great, and communicate pretty well what system was designed for, but they are in no way hard guarantee that the system will be up.