RAID 5 with 4 HDD one Failed how to reassamble the RAID .. not possible unter the GUI

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  • T3sticle
    T3sticle Posts: 13  Freshman Member
    edited December 2018
    but before i do this..
    is there a chance to create a raid 5 out of the 3 disks 2,3,4 just to access the data.
    i have a bad feeling to reassamble the raid with 4 disks as first step
    :)
    sda is the orginal "defective" disk .. now replaced and  in raid 1 status
    SDB disk 2
    SDC Disk 3
    And SDD Disk 4  these three are in Hot Spare status (unter the GUI of the NAS
    correct. ?



  • Mijzelf
    Mijzelf Posts: 2,815  Guru Member
    250 Answers 2500 Comments Friend Collector Seventh Anniversary
    is there a chance to create a raid 5 out of the 3 disks 2,3,4 just to access the data.
    Yes. That's what we are doing, creating a 4 disk raid5 array out of 3 disks and a missing.
    i have a bad feeling to reassamble the raid with 4 disks as first step
    AFAIK that can't be done, here. As the 4th disk doesn't 'fit' in the array, it can't be used in an 'assume-clean' array. So the procedure is, build a degraded 'assume-clean' array, and when that is up, you can add a 4th disk.

    correct. ?
    Yes. Although from the raid headers I can't deduce what happened. Disk 1 was down, so all remaining members had a '.AAA' status. Then you pulled disk 4. What should have happened is that the remaining disks got the '.AA.' status. Disk 4 keeps it's '.AAA' status, as it couldn't be updated. When you put back disk 4, it wasn't accepted, as disks 2 and 3 both had an '.AA.' status, and the raid manager couldn't possibly know what happened to disk 4.

    But, that actual state of the headers is:
    <div>/dev/sdb3:<br>&nbsp;&nbsp;&nbsp; Update Time : Thu Dec 27 22:09:46 2018<br>&nbsp;&nbsp; Device Role : Active device 1<br>&nbsp;&nbsp; Array State : .AAA ('A' == active, '.' == missing)<br>/dev/sdc3:<br>&nbsp;&nbsp;&nbsp; Update Time : Thu Dec 27 22:09:46 2018<br>&nbsp;&nbsp; Device Role : Active device 2<br>&nbsp;&nbsp; Array State : .AA. ('A' == active, '.' == missing)<br>/dev/sdd3:<br>&nbsp;&nbsp;&nbsp; Update Time : Thu Dec 27 22:07:06 2018<br>&nbsp;&nbsp; Device Role : Active device 3<br>&nbsp;&nbsp; Array State : .AAA ('A' == active, '.' == missing)<br></div><div></div>
    I think you pulled the disk at Thu Dec 27 22:09:46 2018. Both remaining disks got an update, but only sdc2 got a 'sdd3 missing' flag. Which is strange.
    Anyway, all 3 disks are not further than 2 minutes 40 out of sync, so even without your story about what actually happened, I would assume this 3 disks contain the needed data to rebuild the array.


  • T3sticle
    T3sticle Posts: 13  Freshman Member
    edited December 2018
    thats the best news at the end of 2018 .. Thank You..
    so i try my best
    ..
    will tell you what happens
  • T3sticle
    T3sticle Posts: 13  Freshman Member
    edited December 2018
    BusyBox v1.19.4 (2017-05-26 16:43:23 CST) built-in shell (ash)
    Enter 'help' for a list of built-in commands.

    ~ # mdadm --stop /dev/md2
    mdadm: error opening /dev/md2: No such file or directory
    ~ # mdadm --stop /dev/md2
    mdadm: error opening /dev/md2: No such file or directory
    ~ # mdadm --create --assume-clean --level=5  --raid-devices=4 --metadata=1.2 --chunk=64K  --layout=left-symmetric /dev/md2 missing /dev/sdb3 /dev/sdc3 /dev/sdd3
    mdadm: /dev/sdb3 appears to be part of a raid array:
        level=raid5 devices=4 ctime=Sun Aug 30 17:00:06 2015
    mdadm: /dev/sdc3 appears to be part of a raid array:
        level=raid5 devices=4 ctime=Sun Aug 30 17:00:06 2015
    mdadm: /dev/sdd3 appears to be part of a raid array:
        level=raid5 devices=4 ctime=Sun Aug 30 17:00:06 2015
    Continue creating array? y
    mdadm: array /dev/md2 started.



    and the nas is Beeping (alert)


  • T3sticle
    T3sticle Posts: 13  Freshman Member
    Oh YEAH
  • T3sticle
    T3sticle Posts: 13  Freshman Member
    only thing to cross the fingers that not one of the disks  spread the wings before the 50 hours are DONE
  • Mijzelf
    Mijzelf Posts: 2,815  Guru Member
    250 Answers 2500 Comments Friend Collector Seventh Anniversary
    Answer ✓
    You can also spent that 50 hours to think about a backup strategy. This episode has shown that data is fragile.
  • T3sticle
    T3sticle Posts: 13  Freshman Member

    :)  Thank you very much for your Help...

    the RAID is back up an running..

    the missing data is now save an copied to another disk.

    We need more people  like you that spend time for the Problems of strangers.. in this

    World today.

    Best regards

    Bernd


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