Copy data from removed jbod disks

hazimozi
hazimozi Posts: 10
First Comment
in Personal Cloud Storage

I had to remove 2x 2TB disks from NSA 325 due to possible hw error. The disks are intact without any failure. They were installed in jbod mode.

Is there any tool I can read the data with?

When I attached the disks via USB rack the volumes are there. The first disk seams readable with accessible file system but the second one has no any fs just the volume.

Any idea?

Best Answers

  • Mijzelf
    Mijzelf Posts: 2,764  Guru Member
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    Answer ✓

    Alas the meaning of JBOD is different for different NAS brands. For a ZyXEL it means 'linear multi disk', which means that the different disks are glued together to one new virtual device. So your first disk contains the first half of the resulting volume, and the second disk the second half.

    Now you can sort of read your first disk, because the header of the filesystem is on the first half, but the second starts in the middle. To read the volume you'll have to assemble the array.

    BTW, the difference between linear multi disk and raid0 is that raid0 is chunked. The first 64k of the virtual disk is on disk 1, the second 64k on disk 2, the third on disk 1, … . This has as advantage that while reading/writing big files you can combine the throughput of both disks.

    Is it possible to attach these volumes to the new NAS somehow?

    Unfortunately not. The partition layout on the NAS series is different from the partition layout on the NSA series, so it's not recognized as a 'familiar' disk. But it is possible to assemble and mount the volume manually, and then it stays mounted till next reboot.

  • Mijzelf
    Mijzelf Posts: 2,764  Guru Member
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    Answer ✓

    Indeed. You have got 2 linear array of 1 disk each.

    So the commands to assemble and mount them could be

    su

mdadm -A /dev/md0 /dev/sda2 
mkdir -p /mnt/myvolume
mount /dev/md0 /mnt/myvolume

mdadm -A /dev/md1 /dev/sdb2 
mkdir -p /mnt/myvolume2
mount /dev/md1 /mnt/myvolume2

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All Replies

  • hazimozi
    hazimozi Posts: 10
    First Comment

    One more... I have got a NSA 326. Started the setup process with those 2 disks, but it says would like to create new volumes. I didn't let to do. But the NAS system is up.

    Is it possible to attach these volumes to the new NAS somehow?

  • Mijzelf
    Mijzelf Posts: 2,764  Guru Member
    250 Answers 2500 Comments Friend Collector Seventh Anniversary
    Answer ✓

    Alas the meaning of JBOD is different for different NAS brands. For a ZyXEL it means 'linear multi disk', which means that the different disks are glued together to one new virtual device. So your first disk contains the first half of the resulting volume, and the second disk the second half.

    Now you can sort of read your first disk, because the header of the filesystem is on the first half, but the second starts in the middle. To read the volume you'll have to assemble the array.

    BTW, the difference between linear multi disk and raid0 is that raid0 is chunked. The first 64k of the virtual disk is on disk 1, the second 64k on disk 2, the third on disk 1, … . This has as advantage that while reading/writing big files you can combine the throughput of both disks.

    Is it possible to attach these volumes to the new NAS somehow?

    Unfortunately not. The partition layout on the NAS series is different from the partition layout on the NSA series, so it's not recognized as a 'familiar' disk. But it is possible to assemble and mount the volume manually, and then it stays mounted till next reboot.

  • hazimozi
    hazimozi Posts: 10
    First Comment

    Thx. So I need a system to let me in via ssh, now the factory system don't let me in.

    Can I start a modded one from back USB ports?

  • Mijzelf
    Mijzelf Posts: 2,764  Guru Member
    250 Answers 2500 Comments Friend Collector Seventh Anniversary

    ? I don't understand the question.

    You can use your 326 to read the disks. Start it without disks, and enable the ssh server. Check if you have ssh access. Shut it down, and insert the disks. Then start it up, login over ssh, and execute

    su
mdadm -A /dev/md0 /dev/sda2 /dev/sdb2

    Now your array should be assembled to a virtual device md0. Then mount it:

    mkdir -p /mnt/myvolume
mount /dev/md0 /mnt/myvolume

    You should be able to see your files with

    find /mnt/myvolume

    But it is also possible that the firmware dives in between handles the filesystem as an USB stick and moves the mountpoint. In that case you can see it in the webinterface and use it as a normal share.

  • hazimozi
    hazimozi Posts: 10
    First Comment

    My bad, finally found the ssh enable menu and the NAS let me in.

    Try to do mdadm and the rest, will feed back.

    Thx

  • hazimozi
    hazimozi Posts: 10
    First Comment

    (my last post disappeared…)

    So, I faced with other difficulties after log in via ssh and tried suggested commands. Here is the result:

    ~ # mdadm -A /dev/md0 /dev/sda2 /dev/sdb2
    mdadm: no RAID superblock on /dev/sdb2
    mdadm: /dev/sdb2 has no superblock - assembly aborted

    Disk /dev/sda: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors
    Units: sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 4096 bytes
    I/O size (minimum/optimal): 4096 bytes / 4096 bytes
    Disklabel type: dos
    Disk identifier: 0xced5416b

    Device Boot Start End Sectors Size Id Type
    /dev/sda1 63 1028159 1028097 502M 8 AIX
    /dev/sda2 1028160 3907024064 3905995905 1.8T 20 unknown

    Partition 2 does not start on physical sector boundary.

    Disk /dev/sdb: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors
    Units: sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 4096 bytes
    I/O size (minimum/optimal): 4096 bytes / 4096 bytes
    Disklabel type: dos
    Disk identifier: 0xf1aeb40b

    Device Boot Start End Sectors Size Id Type
    /dev/sdb1 63 1028159 1028097 502M 83 Linux
    /dev/sdb2 1028160 3907024064 3905995905 1.8T 20 unknown

    Partition 2 does not start on physical sector boundary.

  • Mijzelf
    Mijzelf Posts: 2,764  Guru Member
    250 Answers 2500 Comments Friend Collector Seventh Anniversary

    Can you post the output of

    su
mdadm -E /dev/sd[ab]2

  • hazimozi
    hazimozi Posts: 10
    First Comment
    edited March 4

    Of course yes. But there are some news.
    I tried this:

    ~ # mdadm --assemble --scan
    mdadm main: failed to get exclusive lock on mapfile
    mdadm: /dev/md/NSA325:1 has been started with 1 drive.
    mdadm: /dev/md/0_0 has been started with 1 drive.

    After that I succesfully mounted "NSA325" and "0_0" volumes and could list all the files on those. It seems i didn't make an array of the two disks but installed them individuals but JBOD types.

    the mounted volumes can be acces with winscp, and I initiated succesfull download!

  • hazimozi
    hazimozi Posts: 10
    First Comment

    here is the outout:

    ~ # mdadm -E /dev/sda2
    /dev/sda2:
    Magic : a92b4efc
    Version : 0.90.00
    UUID : 2df9b15b:f7eaf4b3:8b7f4c77:b216125d
    Creation Time : Mon Jan 6 21:23:55 2014
    Raid Level : linear
    Raid Devices : 1
    Total Devices : 1
    Preferred Minor : 0

    Update Time : Mon Jan  6 21:23:55 2014
    
      State : clean

    Active Devices : 1
    Working Devices : 1
    Failed Devices : 0
    Spare Devices : 0
    Checksum : b23ab137 - correct
    Events : 1

       Rounding : 0K

    
  Number   Major   Minor   RaidDevice State

    this 0 8 2 0 active sync /dev/sda2

    0 0 8 2 0 active sync /dev/sda2
    ~ # mdadm -E /dev/sdb2
    /dev/sdb2:
    Magic : a92b4efc
    Version : 1.2
    Feature Map : 0x0
    Array UUID : 54c231fb:f0ace46c:54ec7371:5b06bdee
    Name : NSA325:1
    Creation Time : Fri Dec 1 01:26:30 2017
    Raid Level : linear
    Raid Devices : 1

    Avail Dev Size : 3905993857 (1862.52 GiB 1999.87 GB)
    Used Dev Size : 0
    Data Offset : 2048 sectors
    Super Offset : 8 sectors
    State : clean
    Device UUID : d963be84:b6a21e32:9754916f:1b46a9da

    Update Time : Fri Dec  1 01:26:30 2017
    
   Checksum : 74161f4f - correct
    
     Events : 0

    
   Rounding : 0K

    Device Role : Active device 0
    Array State : A ('A' == active, '.' == missing)

  • Mijzelf
    Mijzelf Posts: 2,764  Guru Member
    250 Answers 2500 Comments Friend Collector Seventh Anniversary
    Answer ✓

    Indeed. You have got 2 linear array of 1 disk each.

    So the commands to assemble and mount them could be

    su

mdadm -A /dev/md0 /dev/sda2 
mkdir -p /mnt/myvolume
mount /dev/md0 /mnt/myvolume

mdadm -A /dev/md1 /dev/sdb2 
mkdir -p /mnt/myvolume2
mount /dev/md1 /mnt/myvolume2

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