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Thread: Add third disk to two disk SOFTWARE raid5?

  1. #1
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    Default Add third disk to two disk SOFTWARE raid5?

    My problem is as follows:
    My old hardware died on me, I replaced it and installed 11.1.
    Due to the hardware failure my RAID array that originally existed out of 3 disks has the third one out of sync, thus effectively reducing it to a RAID5 with only 2 disks.
    As you'll surely agree... my data isn't very safe at the moment and I'd like to add disk #3 to the raid array.

    I can't seem to find any option anywhere in yast to add a disk to an existing array. I was expecting an "Add" button in the third screenshot below (The other 2 are just there so hopefully you can get some information out of it on how to fix it)

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  2. #2
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    Default Re: Add third disk to two disk SOFTWARE raid5?

    Quote Originally Posted by Axeia
    My problem is as follows:
    My old hardware died on me, I replaced it and installed 11.1.
    Due to the hardware failure my RAID array that originally existed out
    of 3 disks has the third one out of sync, thus effectively reducing it
    to a RAID5 with only 2 disks.
    As you'll surely agree... my data isn't very safe at the moment and I'd
    like to add disk #3 to the raid array.

    I can't seem to find any option anywhere in yast to add a disk to an
    existing array. I was expecting an "Add" button in the third screenshot
    below (The other 2 are just there so hopefully you can get some
    information out of it on how to fix it)

    '[image: http://thumbnails9.imagebam.com/2135...121340688.gif]'
    (http://www.imagebam.com/image/41bc0121340688) '[image:
    http://thumbnails2.imagebam.com/2135...221340690.gif]'
    (http://www.imagebam.com/image/be2b6221340690) '[image:
    http://thumbnails12.imagebam.com/213...121340693.gif]'
    (http://www.imagebam.com/image/8a8e5121340693)
    Hi
    What about if you select the device it's self (sdd) and set it to a
    raid file system, can you then add it to the array?

    You may wish to investigate the CLI tool mdadm....

    --
    Cheers Malcolm (Linux Counter #276890)
    openSUSE 11.1 x86 Kernel 2.6.27.7-4-default
    up 1 day 20:40, 2 users, load average: 0.36, 0.28, 0.16
    GPU GeForce 6600 TE/6200 TE - Driver Version: 177.82


  3. #3
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    Default Re: Add third disk to two disk SOFTWARE raid5?

    It's already set to a "OxFD Linux Raid" under the "File system ID" and that's pretty much the only I can do with it.. no option to add it to an existing array.
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  4. #4

    Default Re: Add third disk to two disk SOFTWARE raid5?

    Quote Originally Posted by Axeia View Post
    RAID array that originally existed out of 3 disks has the third one out of sync, thus effectively reducing it to a RAID5 with only 2 disks.
    As you'll surely agree... my data isn't very safe at the moment and I'd like to add disk #3 to the raid array.
    A lot of ppl would lose data with 1 disk failure so you were ahead of the game. But now you're more than twice as likely to have a failure, as 2 disks must stay up, and similar models may start failing all together given similar usage. So you're right to address it.

    RAID5 basically sux...

    RAID10 striping mirrored sets, just needs 1 disk more, and offers higher performance and resilience. You also do 1/2 the Read I/O to fix the volume.

  5. #5
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    Default Re: Add third disk to two disk SOFTWARE raid5?

    I installed "Raid-Monitor" as I stumbled upon it while reading How to install openSUSE on software RAID - openSUSE which seems to make use of the mentioned mdadm.

    But it doesn't give much info.. hell the only thing I can get it to do is display a window with the content below in a textfield.
    Code:
    Personalities : [raid6] [raid5] [raid4] 
    md1 : active raid5 sdc1[1] sdb1[3]
          1953519616 blocks super 1.0 level 5, 128k chunk, algorithm 0 [3/2] [_UU]
          bitmap: 218/466 pages [872KB], 1024KB chunk
    
    unused devices: <none>
    Reading further,
    Code:
    raidhotadd  /dev/md1 /dev/sdd1
    could this be the command?

    Example given is
    (*) raidhotadd is a command to add a new partition to the raid, e.g.:

    raidhotadd /dev/md1 /dev/hda1
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  6. #6
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    Default Re: Add third disk to two disk SOFTWARE raid5?

    Quote Originally Posted by Axeia
    I installed "Raid-Monitor" as I stumbled upon it while reading 'How to
    install openSUSE on software RAID - openSUSE'
    (http://en.opensuse.org/How_to_instal..._software_RAID)
    which seems to make use of the mentioned mdadm.

    But it doesn't give much info.. hell the only thing I can get it to do
    is display a window with the content below in a textfield.
    Code:
    --------------------
    Personalities : [raid6] [raid5] [raid4]
    md1 : active raid5 sdc1[1] sdb1[3]
    1953519616 blocks super 1.0 level 5, 128k chunk, algorithm 0 [3/2]
    [_UU] bitmap: 218/466 pages [872KB], 1024KB chunk

    unused devices: <none>
    --------------------
    Hi
    What about the section called 'Reconstruction'? Also from the cli use;
    Code:
    man mdadm
    This is all the commands and options.

    Make sure you have backed up your data as well.....!!!

    --
    Cheers Malcolm (Linux Counter #276890)
    openSUSE 11.1 x86 Kernel 2.6.27.7-4-default
    up 2 days 0:56, 4 users, load average: 0.45, 0.68, 0.78
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  7. #7
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    Default Re: Add third disk to two disk SOFTWARE raid5?

    from what I can tell
    Code:
    raidhotadd /dev/md1 /dev/sdd
    should do the trick, and mdadm can give a lot of information, but I've no idea what to do with it.

    So it would be awesome if someone with some expertise in this field could tell me whether it's the right command or if I should do something else.. else I guess I'll just try it out as I got the time now to restore things if they get messed up.
    [edit]:
    That's not it at least
    Code:
    raidhotadd /dev/md1 /dev/sdd1
    bash: raidhotadd: command not found
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  8. #8
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    Default Re: Add third disk to two disk SOFTWARE raid5?

    So I got rather brave and performed the following command:
    Code:
    mdadm --add /dev/md1 /dev/sdd1
    Which instantly replied with "mdadm: re-added /dev/sdd1".

    And now I'm hearing the disks perform some read/write actions while the computer is idling.. so my guess is that it's working and I'll just have to wait till it's done. I'll post again when it's done to let you know what happened..
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  9. #9
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    Default Re: Add third disk to two disk SOFTWARE raid5?

    Quote Originally Posted by Axeia
    So I got rather brave and performed the following command:

    Code:
    --------------------
    mdadm --add /dev/md1 /dev/sdd1
    --------------------

    Which instantly replied with "mdadm: re-added /dev/sdd1".

    And now I'm hearing the disks perform some read/write actions while the
    computer is idling.. so my guess is that it's working and I'll just have
    to wait till it's done. I'll post again when it's done to let you know
    what happened..
    Hi
    The following will give you info;

    Code:
    mdadm --detail /dev/md1
    and
    cat /proc/mdstat
    --
    Cheers Malcolm (Linux Counter #276890)
    openSUSE 11.1 x86 Kernel 2.6.27.7-4-default
    up 2 days 17:57, 2 users, load average: 0.13, 0.22, 0.33
    GPU GeForce 6600 TE/6200 TE - Driver Version: 177.82


  10. #10
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    Default Re: Add third disk to two disk SOFTWARE raid5?

    I installed Raid-Monitor earlier and it's showing me probably the same output as that command. At least I know for sure it's rebuilding.
    Code:
    Personalities : [raid6] [raid5] [raid4] 
    md1 : active raid5 sdd1[0] sdc1[1] sdb1[3]
          1953519616 blocks super 1.0 level 5, 128k chunk, algorithm 0 [3/2] [_UU]
          [=======>.............]  recovery = 36.0% (351710592/976759808) finish=122.4min speed=85040K/sec
          bitmap: 133/466 pages [532KB], 1024KB chunk
    
    unused devices: <none>
    Takes some time 3 * 1TB

    Thanks for the help and unless I run into trouble.. which I don't expect to.. case closed.
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