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Thread: RAID 10 implementation

  1. #1
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    Feb 2007
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    RAID 10 implementation

    Hi guys. Looking for some pointers here.

    Trying to create a RAID10 file server, auxiliary storage really.

    This is probably just a really stupid problem on my end, but can't figure it out for the life of me. Seams like basic RAID management really.

    4 disks. All identically partitioned.

    100 MB /boot, RAID1 with 2 spares (I hear you can't use RAID10 for /boot)
    2 GB swap on each disk (not mirrored)
    remainder of disk is /, RAID10

    Everything installed fine.

    So I remove a disk just to see what happens. Just testing everything really.

    And the system can't boot. MDADM says it doesn't have enough drives to start the array. Well, obviously, I failed one on purpose. Shouldn't the system boot anyway? Isn't that the point of having a RAID, in case a drive fails?

  2. #2
    Join Date
    Dec 2007
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    Brazil
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    Xubuntu 12.04 Precise Pangolin

    Re: RAID 10 implementation

    I'm not sure, but I think the clusters deployed with MDADM needs the original number of disks to work, ever. Only RAID 1 can work without the exactly number of disks AFAIK.

    Try to start the RAID cluster and save a file. Remove one disk and format it. Then put it again on cluster and verify if synchronization is working on it.
    "In a wide open world without doors or walls, who needs gates or windows?"
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  3. #3
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    Ubuntu 8.04 Hardy Heron

    Re: RAID 10 implementation

    Raid 10 should still work after a loss of a drive. You may try booting into the live CD and rebuilding it. After its rebuilt and in the OS, then remove a disk to test it.

  4. #4
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    Re: RAID 10 implementation

    Quote Originally Posted by TheGameAh View Post
    And the system can't boot. MDADM says it doesn't have enough drives to start the array. Well, obviously, I failed one on purpose. Shouldn't the system boot anyway? Isn't that the point of having a RAID, in case a drive fails?
    AFAIK, raid1 wont function if one disk fail neither will raid 0 or 10. RAID5 and possibly raid 6 continue to run if one drive fail.

  5. #5
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    Re: RAID 10 implementation

    Here is a good overview of raid arrays.http://www.acnc.com/04_01_10.html Raid 10 has the same fault tolerance as raid 1, which is a mirror. The array will no longer be viable until rebuilt but the data is still there and can be booted as long as grub is installed on that drive.

  6. #6
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    Re: RAID 10 implementation

    And also, Raid 0 is the raid implementation that will not tolerate any failures. One drive dies.....all data gone!

  7. #7
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    Re: RAID 10 implementation

    Raid10 will function in degraded mode if one disk fails.

    See the howto on preventing against one failing disk using raid10 at http://linux-raid.osdl.org/index.php...a_failing_disk

  8. #8

    Re: RAID 10 implementation

    your partitioning looks fine.
    and RAID 10 should boot, i tested this on Debian Etch extensively detaching all the disks, not all at the the same time offcourse
    http://www.songshu.org/index.php/setup-raid-10
    this is what i did and this works.

    i've also been hearing stories that Hardy RAID 1 has a bug, sounds like exactly the issue, you might just want to team up on launchpad for this
    Last edited by songshu; February 21st, 2009 at 10:42 PM.

  9. #9
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    Re: RAID 10 implementation

    Just curious, why RAID 10? RAID 5 would work much better IMHO. You only need 3 disks to do RAID 5, and you can pull a drive with no problems although the array will be degraded.

    -Tim
    www.pcchopshop.net

    Hard to find and obsolete PC and server parts. "If we can't find it, it probably doesn't exist"

  10. #10

    Re: RAID 10 implementation

    Quote Originally Posted by windependence View Post
    Just curious, why RAID 10? RAID 5 would work much better IMHO. You only need 3 disks to do RAID 5, and you can pull a drive with no problems although the array will be degraded.

    -Tim
    its a matter of dispute oftenly but with raid10 you can actually loose 2 disks (as long as long as its not the wrong 2) so slightly more secure.
    at the cost of 50% diskspace instead of 30%

    its faster, really it makes a difference (especially with linux raid in my experience)

    most real problems with raid5 occure when you actually loose a disk and then need to hotswap, usually a disk that has been on stand by will suddenly be put under a big load and this is where percentage wise the moment things bad can happen to a raid5.

    as far as i can tell raid10 will give you a little more performance and slightly more security at the cost of some diskspace and a little flexibility if you would like to increase the array at a later point.

    this all providing your distubution of choice would ship without bugs in their mdadm package........

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