If you’re about to sell or give away a computer, it’s important to ensure that all of your personal data is erased first. This is a pretty simple task when it comes to traditional spinning hard drives, and there are plenty of tools to make sure the drive is completely and securely wiped. Solid State Drives, however, are a different story. SSDs use something called “wear leveling,” which ensures that no one cell gets written to too many times. This is to keep the drive from wearing out, but it also means that it isn’t possible to write over (or erase) every part of the drive.
Keith wants to restore his iPhone back to factory settings without losing his health data. Leo says there are layers of resetting in the iPhone, and it's hard to erase it entirely. But he's had issues with his Apple Watch and getting text messages and wants to try starting over. Leo says to go into settings and start with the lowest level of resetting. He should start with "Reset Network Settings." If that doesn't fix it, he can try the "Reset All Settings." Only the "Erase All Content and Settings" will delete his health data.