Unmountable FS after Data-rebuild

[xyseer]

I have only one parity and 2 disks in my system. Recently one of my disk(disk1) had read errors and the system disabled that disk. I have no choice but to replace that bad disk with a new one. As many topics have said. Just replace disk in the array slot and the system will automatically rebuild data with out any other procedures.

While tragedy happened here. When the rebuilding finished. A notice that "Unmountable: no or wrong filesystem." was on the disk. While I used the btrfs in the former disk so I tried to run "btrfs check" to see whether there was a filesystem error. Unfortunately, the tools shows that "cannot read chunk-tree". I tried lots of things including btrfs rescue but nothing happened. It was stiil unmountable. 

 

Is there any way to bring my data back? There was no valuable logs since I've reboot systems for lots of times.

[JorgeB]

Please post he diagnostics after array start.

[xyseer]

The disk1 reported below when check status of btrfs:

 

Couldn't read tree root
Could not open root, trying backup super
parent transid verify failed on 240418816 wanted 33573 found 33543
parent transid verify failed on 240418816 wanted 33573 found 33543
parent transid verify failed on 240418816 wanted 33573 found 33543
Ignoring transid failure
ERROR: root [1 0] level 2 does not match 0

[xyseer]

Here's the diagnostics from my Unraid

xynas-diagnostics-20230831-1023.zip

[JorgeB]

6 hours ago, xyseer said:

parent transid verify failed on 240418816 wanted 33573 found 33543

This error is fatal, it means some writes were lost, it can happen if a storage device lies about flushing it's write cache, this is usually a drive (or controller) firmware problem.

 

You can try btrfs restore (option #2 here) but doubt it will work the way the fs is, if it does then the device will need to be formatted and the data restore.

[xyseer]

So, you mean that if 'btrfs restore' cannot bring the files back, then all my data will be lost?

(Since I've tried restore yesterday however it cannot restore anything. Even using btrfs-find-root together with btrfs restore in order to manually recover some data has failed😭)

[JorgeB]

7 hours ago, xyseer said:

So, you mean that if 'btrfs restore' cannot bring the files back, then all my data will be lost?

Most likely, you might want and check the old disk, if it's not completely dead most data should be recoverable, ddrescue may help.

[xyseer]

OK, Thanks for your answer and solutions. I'll try ddrescue to bring data.

 

[xyseer]

However, this parity is so sucks and I'm not considering use this raw backup method again. It's so unreliable!

Unraid is so that worse than Raid! I trusted in Unraid so much and it treated my data like that inversely. 

 

[JorgeB]

What happened is not normal, it suggests parity was not in sync or the controller/disk firmware lost some writes when the disk got disabled, possibly best to use xfs with your hardware, it's usually more robust.