(Solved) Disk replacement lost files

[surfshack66]

I had a disk that seemed to be failing. It was recommended to replace it. So I followed the disk replacement process.

 

I let the parity/data rebuild finish, however it seems all of the contents on that drive is no longer available. I still have the original disk, but am wondering what to do from here.

 

Is it possible to reinstall the original drive with all of the data?

 

 

tower-diagnostics-20181208-1957.zip

[JorgeB]

Formatting is never part of a rebuild, there's even a warning about it:

 

 

When a disk is unmountable you need to run a filesystem check, not format, if the old disk didn't fail completely mount it with the UD plugin and copy the data to the array.

[surfshack66]

Thanks @johnnie.black. I will mount the old disk with UD and copy the data back to the array...hopefully.

 

Can you confirm which disk I formatted? I'm pretty sure I formatted the new disk because I received the unmountable warning. (I know now not to do that and instead run a filesystem check)

[JorgeB]

You formatted disk1, the one you were replacing.

[surfshack66]

On 12/9/2018 at 4:11 AM, johnnie.black said:

You formatted disk1, the one you were replacing.

I formatted the new disk..with serial number ending in K3HDVAJB, correct?

 

So the parity/data-rebuild took 10+ hours, and I formatted a new drive before that process, yet I still lost the files. I'm confused how that happened. I did receive a warning before the format, but I didn't do the data-rebuild yet...so no data was on the drive yet, right?

[trurl]

You are confused about the meaning of the word "format". Many people are, thinking that format means something like "prepare this disk for use" (whatever that vague phrase might mean).

 

Format actually means "write an empty filesystem to this disk". That is what it has always meant in every operating system you have ever used.

 

Notice I said that format is a write operation. When you format a disk in the array, Unraid treats that write operation just as it does every other write operation. It updates parity. So after the format, parity agrees that the disk has an empty filesystem. Then rebuilding from parity results in an empty filesystem.

[surfshack66]

Hmmm.. I see now. Thanks @trurl for the explanation.

[JonathanM]

On 12/8/2018 at 8:04 PM, johnnie.black said:

Formatting is never part of a rebuild, there's even a warning about it:

 

 

When a disk is unmountable you need to run a filesystem check, not format, if the old disk didn't fail completely mount it with the UD plugin and copy the data to the array.

@surfshack66, what warning message would have been sufficient for you to stop and reconsider? Would changing the second line to "This is not used to rebuild a failed drive" help at all?

[surfshack66]

@jonathanm I think the warning message was fine. It's the first line that confused me. "Format will create a file system in all Unmountable disks, discarding all data currently on those disks." My replacement disk was Unmountable so I read that and formatted.

 

Also, the comment above is confusing... "When a disk is unmountable you need to run a filesystem check, not format..." 

[itimpi]

1 minute ago, surfshack66 said:

@jonathanm 

Also, the comment above is confusing... "When a disk is unmountable you need to run a filesystem check, not format..." 

It depends why the disk is unmountable.  If it has a corrupt file system then a file system check is needed instead of a format.     If it is unmountable for a different reason then a format IS needed.    The real question is whether UnRAID should be able to automatically distinguish this or not.

[surfshack66]

On 12/10/2018 at 7:31 PM, itimpi said:

It depends why the disk is unmountable.  If it has a corrupt file system then a file system check is needed instead of a format.     If it is unmountable for a different reason then a format IS needed.    The real question is whether UnRAID should be able to automatically distinguish this or not.

Sounds like a nice-to-have feature.

 

How would I know if a disk is unmountable because of a corrupt file system vs a different reason?

[itimpi]

1 hour ago, surfshack66 said:

Sounds like a nice-to-have feature.

 

How would I know if a disk is unmountable because of a corrupt file system vs a different reason?

If a disk previously mounted OK then the most likely cause of the ‘unmountable’ status is a corrupt file system (typically as a result of a write that failed for some reason).  It can also mean the disk is about to fail, but if the SMART attributes look OK then it cannot hurt to perform a file system check as the first course of action.