The data is stored in little ccd cells. It’s recorded as an analog voltage. There is no difference between analog voltages and digital voltages, I’m just using the word analog to establish that the potential is a domain that can vary continuously.

When you read the data, the levels of the voltages are checked and translated to the digital information they represent.

To determine the level of a voltage, a small amount of current is allowed to flow between the two points being measured. It’s a very small amount. Microamps and less.

When you draw current from a charge carrying device the charge, as represented by the potential between its negative and positive terminals, the voltage, decreases.

When the controller in the ssd responsible for reading voltages and assembling them into porno.mov doesn’t get a clear read, it asks again. As the ssd ages, parts of it can be re queried hundreds of times just to get commonly read information into memory like system files.

So the ssd degrades on read, and the user experiences this as “slowness”.

Would rewriting the data fix this problem? Yes. Using either badblocks -n, dd or a program called spinrite, rewriting the data fixes that problem.

Why doesn’t the ssd just do it? Because the ssd only has so many write cycles before its toast. Better to rely on the user or more accurately the host os to dictate those writes than to take on that responsibility.