Volume is down - what to do?

Dear All, 
After a power failure, my NAS326 did not respond and I could not login on NAS on the web. After a factory reset, a managed to get in, but I got the message that the volume is down. (I got two HDDs, but I used only one.)
Based on what I found in earlier posts, I accessed the NAS via SSH and obtained some information. 
Could you please help me interpret what I got? I am a novice.
Is there any way to recover the data?

Thanks,
Gergely














All Replies

  • Mijzelf
    Mijzelf Posts: 2,140
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    Your raid arrays are fine, so I suppose there is a filesystem error in the encapsulated filesystem.
    The 'not mounted' filesystem is /dev/md3. Try a filesystem check:
    su
    e2fsck /dev/md3

    (BTW, when you are using PuTTY for ssh, you can simply select the text with your mouse. Selected text is on the clipboard.)

  • gkovats
    gkovats Posts: 6
    Thank you, Mijzelf!
    I run the commands you suggested and got the following response:

    ~ # e2fsck /dev/md3
    e2fsck 1.42.12 (29-Aug-2014)
    e2fsck: Attempt to read block from filesystem resulted in short read while tryin                             g to open /dev/md3
    Could this be a zero-length partition?
    ~ #

    Do you have any suggestion?
    Gergely
  • Mijzelf
    Mijzelf Posts: 2,140
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    That blockdevice is certainly not zero-length, according to /proc/partitions. Try
    su
    dmesg -c
    e2fsck /dev/md3
    dmesg

    The first 'dmesg -c' will purge the kernel log buffer. The second call to dmesg will show any log messages added as result of e2fsck. I wonder if any I/O errors are logged.

  • gkovats
    gkovats Posts: 6
    There is a buffer I/O error 
    "end_request: I/O error, dev sdb, sector 8261800
    quiet_error: 23 callbacks suppressed
    Buffer I/O error on device md3, logical block 21"


    The result of the last dmesg command follows. Or do you need the result of the first one as well?

    ~ # e2fsck /dev/md3
    e2fsck 1.42.12 (29-Aug-2014)
    e2fsck: Attempt to read block from filesystem resulted in short read while trying to open /dev/md                     3
    Could this be a zero-length partition?


    ~ # dmesg
    ata2.00: exception Emask 0x0 SAct 0x3 SErr 0x0 action 0x0
    ata2.00: irq_stat 0x40000008
    ata2.00: failed command: READ FPDMA QUEUED
    ata2.00: cmd 60/00:08:a0:10:7e/01:00:00:00:00/40 tag 1 ncq 131072 in
             res 41/40:00:a8:10:7e/00:00:00:00:00/00 Emask 0x409 (media error) <F>
    ata2.00: status: { DRDY ERR }
    ata2.00: error: { UNC }
    ata2.00: configured for UDMA/133
    sd 1:0:0:0: [sdb] Unhandled sense code
    sd 1:0:0:0: [sdb]
    Result: hostbyte=0x00 driverbyte=0x08
    sd 1:0:0:0: [sdb]
    Sense Key : 0x3 [current] [descriptor]
    Descriptor sense data with sense descriptors (in hex):
            72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
            00 7e 10 a8
    sd 1:0:0:0: [sdb]
    ASC=0x11 ASCQ=0x4
    sd 1:0:0:0: [sdb] CDB:
    cdb[0]=0x88: 88 00 00 00 00 00 00 7e 10 a0 00 00 01 00 00 00
    end_request: I/O error, dev sdb, sector 8261800
    Buffer I/O error on device md3, logical block 21
    Buffer I/O error on device md3, logical block 22
    Buffer I/O error on device md3, logical block 23
    Buffer I/O error on device md3, logical block 24
    Buffer I/O error on device md3, logical block 25
    Buffer I/O error on device md3, logical block 26
    Buffer I/O error on device md3, logical block 27
    Buffer I/O error on device md3, logical block 28
    Buffer I/O error on device md3, logical block 29
    ata2: EH complete
    ata2.00: exception Emask 0x0 SAct 0x3 SErr 0x0 action 0x0
    ata2.00: irq_stat 0x40000008
    ata2.00: failed command: READ FPDMA QUEUED
    ata2.00: cmd 60/08:08:a8:10:7e/00:00:00:00:00/40 tag 1 ncq 4096 in
             res 41/40:00:a8:10:7e/00:00:00:00:00/00 Emask 0x409 (media error) <F>
    ata2.00: status: { DRDY ERR }
    ata2.00: error: { UNC }
    ata2.00: configured for UDMA/133
    sd 1:0:0:0: [sdb] Unhandled sense code
    sd 1:0:0:0: [sdb]
    Result: hostbyte=0x00 driverbyte=0x08
    sd 1:0:0:0: [sdb]
    Sense Key : 0x3 [current] [descriptor]
    Descriptor sense data with sense descriptors (in hex):
            72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
            00 7e 10 a8
    sd 1:0:0:0: [sdb]
    ASC=0x11 ASCQ=0x4
    sd 1:0:0:0: [sdb] CDB:
    cdb[0]=0x88: 88 00 00 00 00 00 00 7e 10 a8 00 00 00 08 00 00
    end_request: I/O error, dev sdb, sector 8261800
    ata2: EH complete
    ata2.00: exception Emask 0x0 SAct 0x2 SErr 0x0 action 0x0
    ata2.00: irq_stat 0x40000008
    ata2.00: failed command: READ FPDMA QUEUED
    ata2.00: cmd 60/08:08:a8:10:7e/00:00:00:00:00/40 tag 1 ncq 4096 in
             res 41/40:00:a8:10:7e/00:00:00:00:00/00 Emask 0x409 (media error) <F>
    ata2.00: status: { DRDY ERR }
    ata2.00: error: { UNC }
    ata2.00: configured for UDMA/133
    sd 1:0:0:0: [sdb] Unhandled sense code
    sd 1:0:0:0: [sdb]
    Result: hostbyte=0x00 driverbyte=0x08
    sd 1:0:0:0: [sdb]
    Sense Key : 0x3 [current] [descriptor]
    Descriptor sense data with sense descriptors (in hex):
            72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
            00 7e 10 a8
    sd 1:0:0:0: [sdb]
    ASC=0x11 ASCQ=0x4
    sd 1:0:0:0: [sdb] CDB:
    cdb[0]=0x88: 88 00 00 00 00 00 00 7e 10 a8 00 00 00 08 00 00
    end_request: I/O error, dev sdb, sector 8261800
    quiet_error: 23 callbacks suppressed
    Buffer I/O error on device md3, logical block 21
    ata2: EH complete


    Thanks, 
    Gergely



  • Mijzelf
    Mijzelf Posts: 2,140
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    It's a hardware error.
             res 41/40:00:a8:10:7e/00:00:00:00:00/00 Emask 0x409 (media error) <F>
    For some reason the disk cannot provide blocks 21~29 of md3. (And possibly others neither, but e2fsck didn't try further). So for practical use that disk is dead.

    Do you have valuable and unreplaceable data on that disk?
  • gkovats
    gkovats Posts: 6
    edited May 6
    Some of it. Family photos and videos.
    is there any chance to recover at least part of them?
    Do you have any suggestions?
    Might Photorec work?
  • Mijzelf
    Mijzelf Posts: 2,140
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    Yes, PhotoRec might work.
    Basically you have 4 options:
    1. Try to recover the filesystem.
    2. Try to recover the files.
    3. Outsource the recovery.
    4. Bin it.
    On 1: It is possible that the filesystem is still more or less OK. e2fsck (and probably mount) didn't look further than block 21~29, because it was unreadable, and they assumed the volume was no bigger. When you create a bit-by-bit copy of the disk using something like [url=https://www.gnu.org/software/ddrescue/]ddrescue[/url], the copy will at least lack block 21~29 (which means they will contain zeros), but there is a chance that e2fsck will be able to repair the filesystem.
    On 2: Any tool which can recover files without help of the filesystem, and without choking in I/O errors, might recover some files. PhotoRec is one of them.
    On 3: That will cost you at least a few 100 Euros, or the equivalent in your local valuta, without guarantee that it will give something. As far as I know there is no 'no cure no pay' in this business.

  • gkovats
    gkovats Posts: 6
    Thank you, Mijzelf!

    I truly appreciate your help.
    I just checked the documentation of ddrescue. It is written there that "Never try to repair a file system on a drive with I/O errors; you will probably lose even more data."
    My understanding is that the HDD has an I/O problem. Could an attempt to recover the filesystem lead to additional data loss? Or am I misunderstanding something?

    Many thanks,
    Gergely
  • Mijzelf
    Mijzelf Posts: 2,140
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    My understanding is that the HDD has an I/O problem. Could an attempt to recover the filesystem lead to additional data loss?

    Yes. Although any decent filesystem repair tool will cease action on the first I/O error. That's where ddrescue is for. You copy the disk to another one, which doesn't have I/O errors. (I/O errors are hardware errors. The copy will have zero's at the place where the original had I/O errors, but that sectors are at least normal accessible)

  • gkovats
    gkovats Posts: 6
    Thank you, Mijzelf. I see what can I do. 

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