I have 5 errors in my most recent scheduled (uncorrecting) parity check.

I also do scheduled btrfs scrubs and determined the disk and file at fault. I would like to use what's on the parity disk to replace the data that's on the affected disk.

A correcting parity check would update parity with the errored data, which I do not want. I trust my parity for these bits so I'd like to use them to repair the disk's data.

Does Unraid have a way to do this?

Edited February 28Feb 28 by cybersteel8

The only way to replace bits on a data drive from the parity algorithm is to rebuild the disk.

As for your subject line, parity does not contain any of your data, so copying sectors from the parity drive would only get you sectors of parity bits.

Parity by itself can rebuild nothing. Parity plus all other disks are read to calculate the data for a missing or rebuilding disk.

Parity is very simple and it is basically the same concept wherever it is used and however it is implemented. If you're interested follow this link:

https://docs.unraid.net/unraid-os/getting-started/what-is-unraid/

then expand the Software Defined NAS section, then expand the How Parity Works section

59 minutes ago, cybersteel8 said:

determined the disk and file at fault

replace from backup

And likely that your parity sync errors have nothing to do with the corrupt btrfs files anyway. You should probably just correct them.

If you really want to rebuild the disk to see what you get, I suggest not rebuilding on top of the same disk. Use a new disk in case rebuilding from the sync errors just makes thing worse.