> ZFS scrubbing is designed to counter issues that crop up with bit flips caused by extremely unlikely hardware errors and things like cosmic rays - which are extremely rare, but when you have petabyte scale storage, they actually become plausible risks.
Scrubbing has multiple purposes. Sure cosmic rays, but it also helps detect poor cabling (if somehow that didn't throw checksum errors in regular use), wild writes and degrading media.
Reading every sector with filesystem data is similar to a function of SpinRite that seems to read all sectors. Of course, SpinRite won't know if a good read holds bad data. But ZFS scrub doesn't read all sectors. According to claims, it sounds like SpinRite could issue uncorrected reads to a weak sector multiple times, run statistics and guess at the right value and write it back? That seems possibly useful, especially if the drive is likely to reallocate the sector when it's written to. Issuing writes to all sectors of a spinning disk can help the drive firmware with reallocating problematic sectors, although there's free tools to do that.
Scrubbing has multiple purposes. Sure cosmic rays, but it also helps detect poor cabling (if somehow that didn't throw checksum errors in regular use), wild writes and degrading media.
Reading every sector with filesystem data is similar to a function of SpinRite that seems to read all sectors. Of course, SpinRite won't know if a good read holds bad data. But ZFS scrub doesn't read all sectors. According to claims, it sounds like SpinRite could issue uncorrected reads to a weak sector multiple times, run statistics and guess at the right value and write it back? That seems possibly useful, especially if the drive is likely to reallocate the sector when it's written to. Issuing writes to all sectors of a spinning disk can help the drive firmware with reallocating problematic sectors, although there's free tools to do that.