[RAID5] Missing superblocks after restart

  • Dear community,
    another victim of RAID is hoping for your advice :)


    It is concerning RAID5 using 3 disks (sdb,sdc,sdd) which somehow disappeared :/



    Code
    root@overlord:~# cat /proc/mdstat
    Personalities :
    unused devices: <none>


    Code
    root@overlord:~# blkid
    /dev/mapper/overlord-swap_1: UUID="8663f4e6-7f8c-4033-885d-8d08e30104b7" TYPE="swap"
    /dev/sda5: UUID="f0650d86-91f3-477a-8b10-8e3ae13c712f" TYPE="crypto_LUKS"
    /dev/sda1: UUID="dc9db794-79b6-462d-a806-9b621bb5c9b8" TYPE="ext2"
    /dev/mapper/sda5_crypt: UUID="0vOaS2-131i-2Xhd-SWnu-Fo7h-1ORq-7bvYEV" TYPE="LVM2_member"
    /dev/mapper/overlord-root: UUID="9896bb07-cd74-49a1-9420-109ecf3eb612" TYPE="ext4"




  • No joy :/


    Code
    root@overlord:~# mdadm --assemble /dev/md127 /dev/sd[bcd] --verbose --force
    mdadm: looking for devices for /dev/md127
    mdadm: Cannot assemble mbr metadata on /dev/sdb
    mdadm: /dev/sdb has no superblock - assembly aborted
    root@overlord:~# mdadm --assemble /dev/md0 /dev/sd[bcd] --verbose --force
    mdadm: looking for devices for /dev/md0
    mdadm: Cannot assemble mbr metadata on /dev/sdb
    mdadm: /dev/sdb has no superblock - assembly aborted
    root@overlord:~#


    Looking at the disks themselves, this seems like a mistake with the crypto setup /raid5 growing...
    What do you think?




  • I've got the same problem...
    Superblock in MBR gets wiped after every reboot


    Good news first:
    I can still access my data by re-creating the array but:

    • the drive order must be exactly the same like back then when you created the raid

      • maybe you got an old mdadm --detail or /proc/mdstat output where you can see the raiddevice number for the drive letters (given they're still in the same SATA ports and no BIOS settings like SATA mode where changed)
    • all other details like Number of drives, chunk size etc. must match as well, of course
    • assume-clean should be used so it doesnt actually touch the data
    • no guarantee this works for you, if it doesnt most probably all data is lost.

    Then define as much details as possible within the create, mine for example:
    mdadm --create /dev/md/n0rd --chunk=512 --raid-devices=4 --spare-devices=0 --assume-clean --level=5 --name=datacube:n0rd /dev/sda /dev/sdb /dev/sdc /dev/sdd --verbose


    **edit**
    Found a very nice thread at serverfault from 2012 (see 1st answer with highest score)
    This Shane Madden guy literally tries to break the data with attempts of array creations with wrong order, chunk size and so on but still could access the data after all invalid attepmts

    Quote

    Wow. So, it looks like none of these actions corrupted data in any way. I was quite surprised by this result, frankly;
    I expected moderate odds of data loss on the chunk size change, and some definite loss on the layout change. I learned something today.


    The issue:
    Did you switch your mainboard/controller or even did a BIOS update recently?
    I did switch from an old ivy bridge based board to an ASRock Z87E-ITX.


    In my case I can clearly reproduce that its caused by the mainboard :
    Recreating the array as described above > can mount and access my data > reboot > all superblocks missing > mdadm --examine doesnt find anything neither on mbr nor on partition 1 on each drive


    Interestingly though it somehow cleares the superblock but leaves the GPT partition table intact still showing my single FD00 Linux RAID Partition.
    Sometimes it occurs that one single drive out of the array doesnt get affected, mdadm --examine then still shows the superblock as intact and gdisk throws "corrupted GPT table" > but after another reboot this last-man-standing superblock is also wiped


    To make sure its not OMV i've put in my ubuntu OS SSD from the previous machine (which is still running fine with another raid set) created the array/superblocks > rebooted > gone
    Now i've connected one drive via an PCI-E SATA controller > Superblock deleted again... (The same controller worked like a charm with these hard disks in the ivy system)


    Then i tried an older drive no 4k blocks, no GPT table and guess what? > Mainboard didnt wipe it ... so i guess its some weird behaviour during boot initialisation with UEFI and 4k/GPT disks no matter how the device is connected
    Now i started going crazy with the BIOS Settings, AHCI Mode, RAID Mode, even IDE mode, disabling S.M.A.R.T., disabling SATA Power Management, resetting default BIOS settings - all without success

    Drives are 4x brand-new ST8000AS0002 or let's say "almost" new, the array ran completely fine for a quarter in the ivy machine @Ubuntu
    Yes I know Seagate doesnt recommend their Archive series for NAS purposes to sell their expensive Enterprise versions but until the mainboard change I had 0 issues with them.


    Solution?
    My last idea (except using another board) would be giving the partitions /dev/sdx1/ instead of just the whole drive /dev/sdx during array creation.
    Does this write the superblock to the partition itself instead to the MBR (which seems to get wiped) of the disk?? And even more important: will this destroy my existing data on the drives?

    Greetz,
    N0rd

  • Solved the issue for myself by revoking/cancelling the ASRock Z87E-ITX order while still possible.
    New Board is a Gigabyte GA-H97N-WIFI and it doesnt touch the drives during boot like it's supposed to be...


    Re-created the Array with same specs one last time and all data is still there :thumbup:

  • Since i moved from a N54l to a Dell T20, only 2 of 3 Drives mounted to my Array.
    After i restored the Array, everything runs fine until the next reboot.
    Does anybody have the same problem?
    Thanks
    Marcel

  • Solution?
    My last idea (except using another board) would be giving the partitions /dev/sdx1/ instead of just the whole drive /dev/sdx during array creation.
    Does this write the superblock to the partition itself instead to the MBR (which seems to get wiped) of the disk?? And even more important: will this destroy my existing data on the drives?


    I can confirm the above solution.


    I had a mdadm RAID5 over four disks created on /dev/sd[abcd] instead of /dev/sd[abcd]1. This worked fine on my Jetway NF9G. However, moving the RAID to a brand new Asrock N3700 resulted in deleted superblock information. Luckily, I could reassemble knowing the exact order of drives. So no data was lost in the end. Then I degraded the RAID and created a new one using partitions. This is recommended anyway. Several days later a RAID5 is now working properly on the Asrock N3700.

    OMV 3.0.94


    Hardware:
    ASRock N3700-ITX
    1x4GB DDR3-1600 SO-DIMM
    2x4000GB WD Red and 2x4000GB WD Green in mdadm RAID5
    16 GB Mach Xtreme Technology Ultra MX-ES USB 3.0 as root
    Fractal Design Node 304 with PicoPSU

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