A drive is unmountable. Xfs_repair doesn't work. There are way too many errors, like thousands of lines of inode errors. In the end it says:

xfs_repair: phase6.c:1674: longform_dir2_entry_check_data: Assertion parent != 0' failed.

Even during the check, it says:

No modify flag set, skipping phase 5 Inode allocation btrees are too corrupted, skipping phases 6 and 7

I have now removed the disk from the NAS and hooked it up to my PC. I am pretty sure the drive itself is fine and that the source was corruption caused by either bad power or bad SATA cable, which I have both since replaced.

How do I proceed? From my research DDrescue could be helpful, though I have never used it. If it doesn't work I could pay for Rstudio or UFS. Last resort would be photorec, as it doesn't preserve file structure and names.

With the free version of ddrescue I could see some files and folders, though not many, as it's very limited.

16 hours ago, Fedeöä said:

No modify flag set, skipping phase 5

Try again without -n. If it still doesn't work, best bet is using a file recovery tool, like UFS Explorer.

1 minute ago, JorgeB said:

Try again without -n. If it still doesn't work, best bet is using a file recovery tool, like UFS Explorer.

Did that already. Doesn't work. Same error.

Is UFS Explorer the best tool?

Could you provide a good guide I could follow?

I've never used it myself, but it should be pretty straightforward; just select the disk and scan.

I have the demo version of UFS explorer open again. I have now done a full scan. What is the next step?

It shows two File Systems:

SGI XFS ~13TB out of 16TB disk, nearly full

and

Raw recovery result ~315GB

Should I copy just the Raw recovery result? Should I copy both?

An XFS filesystem seems to be present, right? but xfs_repair used to throw errors like crazy. Is the best course of action to copy all data to another drive and reformat the drive with a new filesystem and then add it back to the array and recalculating parity?

Edited October 19, 2025Oct 19 by Fedeöä

19 hours ago, Fedeöä said:

SGI XFS ~13TB out of 16TB disk, nearly full

I would copy this one first.

Thanks. Was able to save the data. Still have to see if it's complete, but the important stuff seems to be there.

On 10/20/2025 at 9:58 AM, JorgeB said:

I would copy this one first.

After copying the data, do I format the drive?

Even though it says not to? I am copying the data to the array while the disk is attached to my PC, so the data ends up on the other drives. I don't have space on my PC, so it's my only option. But this basically means that I can remove the drive and format it through Unraid to avoid having to rebuild parity, right?

As long as all the data has been copied from that drive, you can format it.