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Thread: Raid5 partition not visible after drive pull

  1. #1
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    May 2010
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    Angry Raid5 partition not visible after drive pull

    Hi,

    On Friday I accidentally pulled the sata lead from one of the 4 hard drives in my raid array. I didn't notice that I had done this until the next morning when my server wouldn't boot, and came up with the generic error

    Waiting for device /media/STORAGE.
    Continue waiting, or press S or M etc.
    I turned it off, found the loose cable, and plugged it back in, restarted the computer, still unable to find the device, so went into the manual recovery section. I accessed mdadm, and left it for 8 hours to rebuild the broken array.

    Now, it still won't boot. I have used a liveCD and can see the array fine, but it cannot seem to find the partition on there.

    To further complicate matters, the home folders are stored on the array, so I am unable to actually launch the system at all.

    Does anyone have any suggestions on how to recover the data? Or, how I can move the home folder location back to the system drive, so I can actually boot into the system to try further commands.

    Many Thanks

    Alexander



    Specs:
    4 x 1TB Hitachi sata drives in Raid5 array
    1 x 40GB samsung ide system drive
    1GB ram
    2.4GHz P4 processor
    Ubuntu Server Edition 10.04

  2. #2
    Join Date
    Feb 2007
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    Ubuntu Development Release

    Re: Raid5 partition not visible after drive pull

    Seems like you are in a heap of trouble... when you boot using a LiveCD can you then load mdadm and run this command:

    Code:
    sudo mdadm --assemble --scan
    After that will this work:

    Code:
    sudo mdadm -D /dev/mdxx
    You might have to download and install mdadm while using the Live CD.
    Regards, frank, at http://yantrayoga.typepad.com/noname/
    Homebuilt Lian-Li PC-Q33WB, Intel i7-4790K 4.6GHz, SSDs,32G RAM | Dell Laptop 13.3".
    Oracle VBox w/ WinXP/Win10 running Xara Designer, PaintShopPro, and InDesign CS.

  3. #3
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    May 2010
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    Re: Raid5 partition not visible after drive pull

    Many thanks for your reply. A heap of trouble is an understatement!

    Quote Originally Posted by fjgaude View Post
    Seems like you are in a heap of trouble... when you boot using a LiveCD can you then load mdadm and run this command:

    Code:
    sudo mdadm --assemble --scan
    After that will this work:

    Code:
    sudo mdadm -D /dev/mdxx
    You might have to download and install mdadm while using the Live CD.
    The above method for assembling the array is the way I got it to sync after I replaced the drive. The detail command gives the following info.


    ubuntu@ubuntu:~$ sudo mdadm --assemble --scan
    ubuntu@ubuntu:~$ sudo mdadm -D /dev/md0
    /dev/md0:
    Version : 00.90
    Creation Time : Sat Jul 3 23:22:10 2010
    Raid Level : raid5
    Array Size : 2930287488 (2794.54 GiB 3000.61 GB)
    Used Dev Size : 976762496 (931.51 GiB 1000.20 GB)
    Raid Devices : 4
    Total Devices : 4
    Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Mon Jul 5 22:33:36 2010
    State : clean
    Active Devices : 4
    Working Devices : 4
    Failed Devices : 0
    Spare Devices : 0

    Layout : left-symmetric
    Chunk Size : 64K

    UUID : 809e5bef:0ea34369:cf127344:71531497
    Events : 0.25

    Number Major Minor RaidDevice State
    0 8 32 0 active sync /dev/sdc
    1 8 64 1 active sync /dev/sde
    2 8 16 2 active sync /dev/sdb
    3 8 48 3 active sync /dev/sdd
    The array itself seems fine. Attached is a screenshot of the Disk Utility, showing the "Unknown Filesystem" on the array. It was ext4 before.

    Any further advice? Or on how to move the home folder location?
    Last edited by al090187; July 6th, 2010 at 08:55 PM.

  4. #4
    Join Date
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    Re: Raid5 partition not visible after drive pull

    I'm not sure what file utility you are using to test the array. Most do not understand arrays at all. The image you attached is too small for me to read.

    While in LiveCD you can make a partition on your system disk and then copy the contents of your /home there. But I still think you have to then correct your /etc/fstab file so the OS knows where to load the files.

    Look in /fstab file and notice what it is trying to do to load the OS and the /home directory. Copy and paste the fstab to your next post here.

    Since your array is solid there is hope to get it all running as you wish once again.
    Regards, frank, at http://yantrayoga.typepad.com/noname/
    Homebuilt Lian-Li PC-Q33WB, Intel i7-4790K 4.6GHz, SSDs,32G RAM | Dell Laptop 13.3".
    Oracle VBox w/ WinXP/Win10 running Xara Designer, PaintShopPro, and InDesign CS.

  5. #5
    Join Date
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    Re: Raid5 partition not visible after drive pull

    The picture I uploaded was wrong. I have just changed it for one you should be able to read.

    The fstab doesn't seem to load a /home directory

    # /etc/fstab: static file system information.
    #
    # Use 'blkid -o value -s UUID' to print the universally unique identifier
    # for a device; this may be used with UUID= as a more robust way to name
    # devices that works even if disks are added and removed. See fstab(5).
    #
    # <file system> <mount point> <type> <options> <dump> <pass>
    proc /proc proc defaults 0 0
    # / was on /dev/sda1 during installation
    UUID=54d8aac9-cbf6-4ccf-9218-dfcee0636c8b / ext4 errors=remount-ro 0 1
    # swap was on /dev/sda5 during installation
    UUID=4c3c49bb-8982-4d0c-877b-773f8ca636e6 none swap sw 0 0
    /dev/scd0 /media/cdrom0 udf,iso9660 user,noauto,exec,utf8 0 0
    /dev/md0 /media/STORAGE ext4 nosuid,uhelper=devkit,nodev 0 0
    If I remember rightly, I changed the location of the home folders individually using Webmin. Basically, the hard drives came from a stand alone NAS, and there were folders on the drives with everyones stuff in. Webmin allowed me to change the home location, so the files were easily accessible again from the samba shares, as they were before.

    I think we need to figure out how to tell the computer there is a partition on the drive, without reformatting it.

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