ZFS ZFS file allocation table

G

Gherardo

Hi,

I was experimenting moving ZFS disks from a FreeBSD to a Linux PC and the other way around.

During one of many tests, I exported a disk (single ZFS drive) on Ubuntu and attached to FreeBSD.
FreeBSD saw the disk, I could see it in dmesg, but zpool import didn't do anything.

I tried zpool create test da3 thinking it would give me an error but the command actually worked and it overwrote the original partition.

I know thefiles are still there, given that zfs create took only a couple of seconds and the disk is half full (6TB).

Is there a way to recover the files inside the old structure or the old structure itself?

Thank you in advance!
 
covacat said:
was ubuntu using it as /dev/sda or as /dev/sdaX (did the drive had any partitions ?)
Click to expand...
The disk was originally created under FreeBSD with zpool create pool ada2 and then exported and imported on linux, so I don't think it had any partitions, but tbh I didn't check.
 
You probably destroyed your data. With new uberblocks and labels pointing to the new MOS, you won't really be able to get the old one back (there's a slim chance that maybe the old pool's first labels were offset, such as on a partition you made instead of the whole disk).

Sorry to say, zpool create was an incredibly stupid thing to run if you cared about the data.
 
Gherardo said:
… thinking it would give me an error …
Click to expand...

Good thinking.

I do see protection against casual mistakes:

Code: 
root@mowa219-gjp4-8570p-freebsd:~ # zpool create test /dev/da2p1
root@mowa219-gjp4-8570p-freebsd:~ # lsblk da2
DEVICE         MAJ:MIN SIZE TYPE                                          LABEL MOUNT
da2              2:54  965M GPT                                               - -
  <FREE>         -:-   1.0M -                                                 - -
  da2p1          2:44  964M freebsd-zfs                             gpt/FreeBSD <ZFS>
root@mowa219-gjp4-8570p-freebsd:~ # zpool export test
root@mowa219-gjp4-8570p-freebsd:~ # zpool create oops /dev/da2    
invalid vdev specification
use '-f' to override the following errors:
/dev/da2 is part of exported pool 'test'
root@mowa219-gjp4-8570p-freebsd:~ # zpool create oops /dev/da2p1
invalid vdev specification
use '-f' to override the following errors:
/dev/da2p1 is part of exported pool 'test'
root@mowa219-gjp4-8570p-freebsd:~ # man zpool-labelclear  
root@mowa219-gjp4-8570p-freebsd:~ # zpool labelclear /dev/da2
use '-f' to override the following error:
/dev/da2 is a member of exported pool "test"
root@mowa219-gjp4-8570p-freebsd:~ # zpool import test && zpool destroy test
root@mowa219-gjp4-8570p-freebsd:~ # zpool labelclear /dev/da2
root@mowa219-gjp4-8570p-freebsd:~ #

(I assume that you did not add -f to force creation.)


Gherardo said:
… overwrote …
Click to expand...

This can't help to recover data, but the image at <https://forums.freebsd.org/posts/547434> should help you to visualise the four areas where labels would have been written.
 
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