Recover ZFS data

Question

Context/Hardware:

HP microserver gen8
1x1TB - standalone, 2x4TB Raid
1x16GB iLO SDCARD with Debian + OpenMediaVault

Event:

SDCARD failure
restarted server and installed Ubuntu on 1TB drive

Consequences:

ZFS not accessible anymore

root@fremen:~# sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL
NAME   FSTYPE       SIZE MOUNTPOINT                    LABEL     
sda    zfs_member 931,5G                               
└─sda1 ext4       931,5G /                             
sdb    zfs_member   3,7T                               
└─sdb1 zfs_member   3,7T                              
sdc    zfs_member   3,7T                               
└─sdc1 zfs_member   3,7T                               
sdd                 5,7G

root@fremen:~# zpool import -D -f 
no pools available to import

root@fremen:~# file -s /dev/sd?1
/dev/sda1: Linux rev 1.0 ext4 filesystem data, UUID=9c46f52c-b529-4c39-a23b-819726f79146 (needs journal recovery) (extents) (64bit) (large files) (huge files)
/dev/sdb1: data
/dev/sdc1: data

Disks seem to be still on the ZFS pool but no data is accessible.

What to do in this situation? It is a friend's setup and I can connect remotely to the machine. I do not want to create a new pool as it will destroy data on ZFS volumes. As I cannot find pools on disks zdb cannot be used.

@MichaelHampton: Even without '-D' there is no available pool. — Daniel Voina, Mar 01 '19 at 19:32
That's really odd. Was there actually a zpool there? Did someone erase it? You might need to restore from backup. — Michael Hampton, Mar 01 '19 at 19:57
Indeed, it is odd. The only idea that I have right now is that the pool info was written on the iLO sdcard and now cannot be accessed. I'm wondering how to dig deeper for data. Unfortunately I couldn't find any tool able to do low level disk inspection (a la testdisk) so that I can recover some of his files. — Daniel Voina, Mar 01 '19 at 20:03

Daniel Voina · Answer 1 · 2019-03-21T05:05:00.030

3

Michael Hampton comments were the solution for this.

It turns out that OMV in fact didn't use ZFS at all but just marked the drives as ZFS members.

I have dd-ed one of the drives and on the image I ran testdisk. It turned out that there was a 0x0700 partition on the disk. Wrote a new partition table with testdisk and mounted it in loop. It turned out to be an ext4 partition with corrupted journal. After fixing the errors I was able to salvage all the data. Hence I did the same on the physical disks, got the data back.

edited Mar 21 '19 at 05:05

answered Mar 13 '19 at 09:47

Daniel Voina

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1
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Thanks for sharing the method of using dd first and working with the image. That's really something I'll remember forever. – Louis Waweru Mar 21 '19 at 05:27

Recover ZFS data

1 Answers1