I have 87 parity errors since a few months ago when it was previously 0. I don’t know why that is the case….

But so far I have not elect to overwrite parity drive, and is deciding to upgrade to a bigger drive and to rebuild from from parity.

However is there a way to see the range of files that’s not matching over those parity errors? It should be technically possible right? This way I can decide to keep parity data or overwrite it during the next parity check.

Unless you have checksums, you have no way of knowing which files are 'broken'. If you're showing errors, it's because the zeros and ones on the disk don't match what the parity calculation is returning.

Unraid should have the information of what files are in that mismatch parity block correct?

No, parity doesn't contain any file information, it only knows it was expecting a 1 and got a 0 from a particular sector on the disk, not what part of which file occupied that sector (it won't know which is the correct bit, the 1 on parity or the 0 from the array disk). If you've had an unclean shutdown, you can just run a correcting parity check to sync parity again, chance for corruption is lower. But, if it just suddenly started showing errors, you need to figure out why (bad disk, bad cable, bad RAM) before you continue.

So now I don’t know if it is parity drive bad or the array is bad. With 87 parity errors, how can I go about deciding and how do I set it to use array data or to use parity data?

4 hours ago, CyberMew said:

So now I don’t know if it is parity drive bad or the array is bad. With 87 parity errors, how can I go about deciding and how do I set it to use array data or to use parity data?

The parity errors don't tell you if a drive is bad or not, either parity or array, the errors are the number of differences from what the parity drive has calculated for the value of a particular sector. The errors can be from bad RAM, cables, random corruption or other hardware issues, or usually power disruption while writing. You'll need to interrogate your disks to make sure they're OK hardware wise, then re-sync parity - hoping whatever was in those 87 sectors was just out of sync or not important if the data was actually corrupted.

This is a good reminder that parity is for redundancy, not data protection. It has no idea what's on your disks, and can only rebuild a disk based on whatever sector info it's got stored.