[gruez]

>My understanding based on my readings of the previous post is there are no hardware level checks

There are "hardware level checks", it's just that they might assume regular usage. If your SSD is turned on regularly (eg. a few hours a day at least), your files are probably fine, even if you never read/scrub your rarely read files. If it is infrequently used, you're right that you probably have to do an end-to-end scan to make sure everything gets checked and possibly re-written.

[Tempest1981]

Is the same true for USB flash drives? Do they rely on the OS to scrub/refresh them?

[kasabali]

"probably" does the heavy lifting here.

[gruez]

I mean, obviously? SSDs and HDDs randomly fail for all sorts of reasons beyond random bitflips, so properly working ECC isn't enough to guarantee your files are "fine". Even if you're using something like ZFS, it's possible for the one of the underlying drive to experience ECC errors, and have another drive fail before that can caught. If your parity factor is 1 or less (eg. RAIDz1), you'll also experience data loss.