QNAP Mounting RAID6 after reboot and "DISK MISSING"

Quick version

  • State: When QNAP boots into the initialization dialog (the one you see when you first setup your QNAP) and then switches to "DISK MISSING" screen but SSH can still be used to connect to it (using the old credentials *strange*)
  • Goal: Mount your RAID and backup all data!
  • Solution:
    # assemble your RAID
    mdadm /dev/md777 --assemble /dev/sd[abcd]3 
     
    # my RAID had a logical volume on on it (LVM); so active the volume group    
    vgchange -a y
     
    # prepare for mounting                              
    mkdir /mnt/md777
     
    # aaand mount (check /dev/mapper for available logical volumes first)
    mount -t ext4 /dev/mapper/vg1-lv1 /mnt/md777
  • Next thing you wanna do is probably rysnc stuff from your RAID to a backup drive. Enabling the dir_index seems to help a lot for folders with many small files (e.g., thumbnails):
    tune2fs -O dir_index /dev/vg1/lv1
    e2fsck -D /dev/vg1/lv1

    I found this here.

Some notes:

  • --assemble simply sets up the RAID to be accessible. It is a command issued by the operating system on each system start anyway (if everything goes well). So it is safe to use without worrying about breaking the RAID.
  • For some reason or another QNAP seems to put a RAID on sdX3 by default (where X can be a,b,c, ... depending on your system setup).

Background

My QNAP acted strange (not taking over settings, acting slugishly, etc.) so I tried to reboot. After half an hour it was still in the rebooting screen so I tried to login again in another tab. It worked but the admin was a regular user now. I waited some more. Then I got impatient and shut down the thing with the power button. Bad idea! But I did not know what else to do.

Afterwards the QNAP would boot into the initialization screen (when you first setup the QNAP). Interestingly enough SSH still worked with my custom admin password (not with admin:admin as is default for a new QNAP). Now, I wanted to backup my data so I had to check if my RAID was still available. With a little bit of help from Google I found several great resources telling me that my RAID was generally OK. So I had to mount it. However, none of the resources really told me how. In the end I came up with the really simple (when you know what you are doing) set of commands listed above. Also I list some resources that were very helpful below.

Happy that data is back, but sooo much time wasted ;(

Resources

  • This gave me all the commands for checking my RAID and working with logical volumes:
    https://forum.qnapclub.de/thread/31872-gel%C3%B6st-singledisk-mounten-auf-selbem-nas/?pageNo=1
  • This showed me how to mount a logical volume in the first place. The only thing that was missing was the -t ext4 part:
    https://www.svennd.be/mount-unknown-filesystem-type-lvm2_member/
  • This have the hint that my RAID was on sd[abcd]3:
    https://mensfeld.pl/2015/02/recovering-qnap-nas-lost-data-when-nas-not-starting-properly/
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