How does bitrot protection actually work?

StephenB wrote:
... If you are concerned about the impact of non-ecc memory, then perhaps buy a readynas that has ecc (e.g., the RN516)

I already have 3 ReadyNAS without ECC, so that is not an option until my next purchase.

I understand that bad memory can corrupt anything it writes, but most of my data is write once, save a long time, read often. Business records, photos, etc.

My concern is turning the bit rot protection on and then, due to bad memory, having every checksum fail during a scrub. This could conceivably cause a re-write of an entire disk with the bad memory. Then in one shot I have corrupted everything.

What do you think?