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Thread: Mdadm raid 5 add drive

  1. #1
    Join Date
    Oct 2008
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    Mdadm raid 5 add drive

    Hi this is a simple question and i'm sure there is a simple answear but i'm just not finding it.

    I created a Raid 5 array with 4x500gb no hot spare all used to give array size 1.5tb, its all working.

    Now i want to test the raid 5, so i power off the system and pull one of the drives power then restart.

    Raid is still avaiable now

    - Should the array have booted without any warning?

    I power off, connect the drive back and boot the array it is still active

    i run mdadm --examine /dev/sdd1

    /dev/sdd1:
    Magic : a92b4efc
    Version : 00.90.00
    UUID : d676c305:563cfb40:e368bf24:bd0fce41
    Creation Time : Fri Oct 17 19:20:40 2008
    Raid Level : raid5
    Used Dev Size : 488383936 (465.76 GiB 500.11 GB)
    Array Size : 1465151808 (1397.28 GiB 1500.32 GB)
    Raid Devices : 4
    Total Devices : 4
    Preferred Minor : 0

    Update Time : Sun Oct 19 19:48:19 2008
    State : active
    Active Devices : 4
    Working Devices : 4
    Failed Devices : 0
    Spare Devices : 0
    Checksum : 256800fa - correct
    Events : 0.7

    Layout : left-symmetric
    Chunk Size : 64K

    Number Major Minor RaidDevice State
    this 3 8 49 3 active sync /dev/sdd1

    0 0 8 1 0 active sync /dev/sda1
    1 1 8 17 1 active sync /dev/sdb1
    2 2 8 33 2 active sync /dev/sdc1
    3 3 8 49 3 active sync /dev/sdd1
    i then run mdadm --examine /dev/sda1

    /dev/sda1:
    Magic : a92b4efc
    Version : 00.90.00
    UUID : d676c305:563cfb40:e368bf24:bd0fce41
    Creation Time : Fri Oct 17 19:20:40 2008
    Raid Level : raid5
    Used Dev Size : 488383936 (465.76 GiB 500.11 GB)
    Array Size : 1465151808 (1397.28 GiB 1500.32 GB)
    Raid Devices : 4
    Total Devices : 4
    Preferred Minor : 0

    Update Time : Sun Oct 19 23:08:09 2008
    State : clean
    Active Devices : 3
    Working Devices : 3
    Failed Devices : 1
    Spare Devices : 0
    Checksum : 25682ff3 - correct
    Events : 0.42

    Layout : left-symmetric
    Chunk Size : 64K

    Number Major Minor RaidDevice State
    this 0 8 1 0 active sync /dev/sda1

    0 0 8 1 0 active sync /dev/sda1
    1 1 8 17 1 active sync /dev/sdb1
    2 2 8 33 2 active sync /dev/sdc1
    3 3 0 0 3 faulty removed
    i try mdadm --examine /dev/sdb1 and mdadm --examine /dev/sdc1 they all say /dev/sdd1 is faulty removed but when i run mdadm --examine /dev/sdd1 it says active sync?

    - so is the drive faulty or active? If i pull another drive would i kill the array?

  2. #2
    Join Date
    Oct 2008
    Beans
    5

    Re: Mdadm raid 5 add drive

    well looks like i gotthe array rebuilding need to runthe assemble mode first then the add command.

    Still reckon it should not have mounted a degraded array but at least i know it was working

    now just have to wait 9 hours for the rebuild....

  3. #3
    Join Date
    Feb 2007
    Location
    Cameron Park CA USA
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    4,419
    Distro
    Ubuntu Development Release

    Re: Mdadm raid 5 add drive

    A raid5 array mounts and runs, but with degraded performance, okay with one drive missing.

    You use the -D command to see the health of the array.

    And use this command to watch an array re-build:

    Code:
    sudo watch cat /proc/mdstat
    Here's some stuff I used to learn from:

    http://shsc.info/LinuxSoftwareRAID
    /usr/share/doc/mdadm/FAQ.gz and md.txt.gz
    http://blog.tcg.com/tcg/2006/04/recovering_raid.html
    http://tldp.org/HOWTO/Software-RAID-HOWTO.html

    Good luck and let us know how you are doing.
    Regards, frank, at http://yantrayoga.typepad.com/noname/
    Homebuilt Lian-Li PC-Q30X Intel i5-4670K 4.0GHz, SSDs, 16G RAM | Dell laptop E1505n, netbook 10n
    Oracle VBox w/ WinXP Pro running Xara Designer, PaintShopPro, and InDesign CS.

  4. #4
    psusi is offline Ubuntu addict and loving it
    Join Date
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    Orlando, FL
    Beans
    3,980
    Distro
    Ubuntu Development Release

    Re: Mdadm raid 5 add drive

    Yea, use -D to see the status of the array, rather than examining each drive. The faulty drive does not know it was faulty and removed because it was not connected at the time.

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