So i did a very dumb thing.

I have 4 16TB drives in my unraid server, 3 data, and 1 parity. 2 zfs, 1 xfs, 1 parity.

I wanted to convert the remaining xfs drive to zfs.

I recalled doing this early on when i had 1zfs and 2 xfs.

So i stopped the array, removed the xfs drive from the config, and started the array, and it emulated the missing drive like usual. I then stopped the array, added the xfs drive back, and changed the fs type to zfs in the config, and started the array. The disk showed not mountable, so, and heres the dumb dumb move, i formatted it. I now have missing files. Is there any hope? It does try to rebuild data, but from what im reading, formatting a drive kinda nukes the parity of said drive.

PLEASE HELP!

Am i SOL??

Yep. You NEVER format a drive that has data you need. That's not at all how you do a filesystem conversion.

Best chance at this point is file recovery software like UFS explorer.

Edited July 1, 20251 yr by Kilrah

sorry, your SOL once formatted unless using very expensive tools and software. (the cost is not worth it) the data is gone after a format.

Since this is disk not ssd / nvme cell the data technically still exists on disk in a low level area and technically data can be recovered but not easily and not free... You are better off taking the loss of data in this situation.

What happens when you format?

• Formatting a disk essentially resets the file system, which is like a table of contents for the disk, making the data inaccessible through normal means. 

  • kinda... (imagine that there is a small ssd chip on the HDD disk controler telling the PC how and where to go to find this data... this chip gets erased when you format...)

• However, the data itself is usually not immediately erased and remains on the disk until new data overwrites it. 

• A quick format only erases the file system, while a full format may overwrite the data with zeros, making recovery more difficult. 

Edited July 1, 20251 yr by bmartino1
Data - Typo

Dang. Gotcha. If theres a tool that rebuilds the file table, would i be able to run that on the drive and then recalculate parity? Would unraid pick up the files and put them with the rest in the /mnt/user folder? Or would my best shot be getting a seperate drive to put in place of the formatted one, recover files on a pc, and transfer them onto the fresh drive/array?

1 minute ago, bmartino1 said:

sorry SOL opnce formated unless using very expensive tools and software. (the cost is not worth it) the data is gone after a format.

Since this is disk not ssd / nvme cell the data technicaly still exists on disk in a low level area and technicaly data can be recoved but not easily and not free.. Your better off taking the loss of data in this situation.

What happens when you format?

• Formatting a disk essentially resets the file system, which is like a table of contents for the disk, making the data inaccessible through normal means. 

  • kinda... (imagine that there is a small ssd chip on the HDD disk controler telling the PC how and where to go to find this data... this chip gets erased when you format...)

• However, the data itself is usually not immediately erased and remains on the disk until new data overwrites it. 

• A quick format only erases the file system, while a full format may overwrite the data with zeros, making recovery more difficult. 

Gotcha. How much we talking? I lost a good 14TB of data here that i dont think there's a way to tell which files were lost..

2 minutes ago, EggMan said:

Dang. Gotcha. If theres a tool that rebuilds the file table, would i be able to run that on the drive and then recalculate parity? Would unraid pick up the files and put them with the rest in the /mnt/user folder? Or would my best shot be getting a seperate drive to put in place of the formatted one, recover files on a pc, and transfer them onto the fresh drive/array?

Some services range to $$$ thousands of dollars... most don't recvoer al the data. adn its take forever when placed in the low level to access data form disks... Theres a few youtube video over it . esentail you want a $$$ thosudand dollar piece of equipment that can do disk foresics....

Regarding teh recaculate pariity...

good question IDK. Its hard to explain and go over recovery opyion when this occurs. again its better to think taht the drive is dead and with it all the data on it.

This is why its important to have backups.

In thory your better off turning off the machine and pulling the HDD in question with another machine. If you have parity and d1 setup correctly you can recover d1 depending on how your array is setup.

review docs
https://docs.unraid.net/legacy/FAQ/Parity/

https://www.youtube.com/watch?v=1orfWpekkqw&pp=0gcJCfwAo7VqN5tD

1 hour ago, bmartino1 said:

Some services range to $$$ thousands of dollars... most don't recvoer al the data. adn its take forever when placed in the low level to access data form disks... Theres a few youtube video over it . esentail you want a $$$ thosudand dollar piece of equipment that can do disk foresics....

Regarding teh recaculate pariity...

good question IDK. Its hard to explain and go over recovery opyion when this occurs. again its better to think taht the drive is dead and with it all the data on it.

This is why its important to have backups.

In thory your better off turning off the machine and pulling the HDD in question with another machine. If you have parity and d1 setup correctly you can recover d1 depending on how your array is setup.

review docs
https://docs.unraid.net/legacy/FAQ/Parity/

https://www.youtube.com/watch?v=1orfWpekkqw&pp=0gcJCfwAo7VqN5tD

What would the correct parity setup look like? When i formatted the drive, would that have caused the parity to update then and there? I would expect that large of a change to take essentially 14TB of parity recalculation, but i could definitely be mistaken

based on your layout

Unraid array:
D1: - xfs

parity to disk 1: - xfs

Pool Devices:
?cache:- 2 ZFS Mirror

"I have 4 16TB drives in my unraid server, 3 data, and 1 parity. 2 zfs, 1 xfs, 1 parity."

so in theory the parity drive can rebuild disk 1

It is for the unrad array parity crazyness I elected to go ZFS only as its easeier to manupilate and do things with zfs... although to move form a zfs mirror to a raidz1 a complete reformat needs to happen...

SO i would advise you to revert the setup.

asuming your zfs is not the disk that lost data. and only d1 and parity were changed.

a picture of you main tab will help here.

2 minutes ago, bmartino1 said:

based on your layout

Unraid array:
D1: - xfs

parity to disk 1: - xfs

Pool Devices:
?cache:- 2 ZFS Mirror

"I have 4 16TB drives in my unraid server, 3 data, and 1 parity. 2 zfs, 1 xfs, 1 parity."

so in theory the parity drive can rebuild disk 1

It is for the unrad array parity crazyness I elected to go ZFS only as its easeier to manupilate and do things with zfs... although to move form a zfs mirror to a raidz1 a complete reformat needs to happen...

SO i would advise you to revert the setup.

asuming your zfs is not the disk that lost data. and only d1 and parity were changed.

sorry for the misunderstanding. All 4 drives are a part of the same "pool" (i forget what the unraid technology is called that doesn't stripe the data and just distributes the files via most empty disk first)

1 parity calculated against 3 drives

6 minutes ago, bmartino1 said:

a picture of you main tab will help here.

Ill get that asap after i get back. I shut the server down because i wanted to halt any more screwing up

Also, am i right in assuming that there is no way to tell which specific files were lost? Asides from browsing the remaining files and trying to remember what used to be there?

46 minutes ago, EggMan said:

Also, am i right in assuming that there is no way to tell which specific files were lost? Asides from browsing the remaining files and trying to remember what used to be there?

correct, not that i'm aware of anyways.

Here's the setup. Disk 3 is the one that i've lost the data on. I've removed it from the server for the time being. Array is stopped. The most I allowed it to "rebuild" the array is ~5%, so I'm hopeful that there is still a significant amount of data remaining hidden on disk 3

6 hours ago, bmartino1 said:

Some services range to $$$ thousands of dollars... most don't recvoer al the data. adn its take forever when placed in the low level to access data form disks... Theres a few youtube video over it . esentail you want a $$$ thosudand dollar piece of equipment that can do disk foresics....

Regarding teh recaculate pariity...

good question IDK. Its hard to explain and go over recovery opyion when this occurs. again its better to think taht the drive is dead and with it all the data on it.

This is why its important to have backups.

In thory your better off turning off the machine and pulling the HDD in question with another machine. If you have parity and d1 setup correctly you can recover d1 depending on how your array is setup.

review docs
https://docs.unraid.net/legacy/FAQ/Parity/

https://www.youtube.com/watch?v=1orfWpekkqw&pp=0gcJCfwAo7VqN5tD

with how it is setup in the image above, would I be able to safely let unraid rebuild the array using parity? or would parity have been changed when I formatted disk 3?

some more questions regarding this:

does the selected disk file system matter? (zfs vs the original xfs)

when it is rebuilding, should I expect to see valid "USED" and "FREE" calculations? or should I expect to the the "Device unmountable: no valid file system" message during the rebuild?

the only thing i've noticed right away as far as missing data is some docker compose files regarding an instance of mailcow, but then again, I haven't dug too far.

If said files aren't showing when the missing disk is being emulated, is it safe to assume that they wont reappear after the full data rebuild?

P.S. - I really appreciate your help! Thank you!

potentially adding some clarity to the timeline of events and what I did:

Stop Array

go to Disk 3 Settings

Change "File system type" from "XFS" to "ZFS"

Applied changes

Start Array

data rebuild starts, disk 3 shows "Unmountable: Unsupported or no file system". There are high writes to disk 3, and high reads on disks 1, 2, and parity.

Stop Rebuild

I Format disk 3

it formats it as ZFS

I restart the server

I start the array

data rebuild starts. disk 3 shows that it is mounted and There are high writes to disk 3, and high reads on disks 1, 2, and parity, just like before.

I try to start mailcow.

I notice files are missing.

I stop the rebuild.

I stop the array.

I go back to the settings for disk 3 and change the file system type from "ZFS" to "XFS"

I start the array in maintenance mode

I press the "Sync" button to initiate the data rebuild

once again data rebuild starts. disk 3 shows "Unmountable: Unsupported or no file system". There are high writes to disk 3, and high reads on disks 1, 2, and parity, just like before.

I let it do its thing for a bit

it reaches ~5.5% rebuilt

I still dont see the mailcow files, so my belief that the data is all still there is very gone

I decide that I've probably done enough damage and should really not be winging it and I reach out here.

Another thought im having is: Since I formatted the drive AFTER making unraid start rebuilding data the first time, would it have possibly kept the parity drive in like a read-only mode, keeping it unchanged since unraid was using it to restore disk 3 with the file system type change?

@JorgeB Thoughts

You can try UFS explorer, the free trial should show what it can recover, app costs around $60

6 minutes ago, JorgeB said:

You can try UFS explorer, the free trial should show what it can recover, app costs around $60

Gotcha.

Do you see any downside to installing a separate 16tb drive into the array, in place of the one I formatted, and having it rebuild to see if unraid would rebuild it "into the drive from before all this"

You can, it will rebuild the new filesystem, the same thing you see on the emulated disk.

50 minutes ago, EggMan said:

Do you see any downside to installing a separate 16tb drive into the array, in place of the one I formatted, and having it rebuild to see if unraid would rebuild it "into the drive from before all this"

Not much point really. The moment you formatted the drive then parity was updated to reflect this. As was mentioned all a rebuild will do is make a physical drive match the emulated one.

Gotcha. So.. when the replacement drive comes in... just pop it in and let it rebuild (Just to get the array back to normal operation)? Does the file system in the disk settings matter at this stage since it is getting rebuilt from parity?

It will be rebuilt as the emulated disk shows currently, if you change the filesystem to a different one, it will be unmountable until reformatted.

5 minutes ago, JorgeB said:

It will be rebuilt as the emulated disk shows currently, if you change the filesystem to a different one, it will be unmountable until reformatted.

so set it to zfs, let it rebuild, and then copy and recoverable data back. Did i get that right?

You can do that.