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Thread: mdadm partiton not large enough to join array

  1. #1

    Default mdadm partiton not large enough to join array

    I've used Linux on and off for the last many years, mainly as dual boot or as Virtual Machines, but when I decided to build a Dev Laptop I though I'd bite the bullet and put Linux on as the base OS.

    In the past I've had issues so thought I'd use RAID to give some resilience, after a bit of head scratching I found the following article Multi HDD/SSD Partition Scheme.

    In summary it advises building 'nested' arrays so you end up with something like the following

    Code:
    md6 - /dev/sda1
        - /dev/md60
    
    md60 -/dev/sdb1
         -/dev/sdc1
    I tried that using an Ubuntu LiveCD, and managed to build the arrays fine, however installing to them was a nightmare, and I never managed to get it working (failed during install). I then moved on to try Debian, and although it installed I couldn't get the drivers for my graphics card to work.

    So onto the third distro (suse) and although it got father but appeared to fail when it tried to assemble the RAID. So I though I'd simplify it by only creating the top level RAID (md6) with the one partition and with one device (so it didn't think it was degraded).

    So I now have a fully working Suse install!!!

    However I don't have a RAID. so I tried to assemble the raid,
    Code:
    mdadm /dev/md6 --add --write-mostly /dev/md60
    or (as some one said it worked this way...
    Code:
    mdadm --add /dev/md6 --write-mostly /dev/md60
    also tried with and without --write-mostly but always got
    Code:
    mdadm: /dev/md60 not large enough to join array
    so a quick look at mdadm --detail gave the following...
    Code:
    /dev/md6:
            Version : 1.2
      Creation Time : Sun Apr 27 14:42:13 2014
         Raid Level : raid1
         Array Size : 204341248 (194.88 GiB 209.25 GB)
      Used Dev Size : 204341248 (194.88 GiB 209.25 GB)
       Raid Devices : 1
      Total Devices : 1
        Persistence : Superblock is persistent
    
        Update Time : Fri May  9 20:38:51 2014
              State : clean 
     Active Devices : 1
    Working Devices : 1
     Failed Devices : 0
      Spare Devices : 0
    
               Name : linux:6
               UUID : b24522f2:8622c47b:be61720b:e69b9dfd
             Events : 23
    
        Number   Major   Minor   RaidDevice State
           0       8       35        0      active sync   /dev/sdc3
    and
    Code:
    /dev/md60:
            Version : 1.2
      Creation Time : Fri May  9 20:21:00 2014
         Raid Level : raid1
         Array Size : 204343296 (194.88 GiB 209.25 GB)
      Used Dev Size : 204343296 (194.88 GiB 209.25 GB)
       Raid Devices : 1
      Total Devices : 1
        Persistence : Superblock is persistent
    
      Intent Bitmap : Internal
    
        Update Time : Fri May  9 20:35:21 2014
              State : active 
     Active Devices : 1
    Working Devices : 1
     Failed Devices : 0
      Spare Devices : 0
    
               Name : hotBlack.ons:60  (local to host hotBlack.ons)
               UUID : 39249c62:f41412c9:b1149c7d:fe4222a0
             Events : 2
    
        Number   Major   Minor   RaidDevice State
           0       8        7        0      active sync   /dev/sda7
    so that looks like

    Code:
    md6  Array Size : 204341248 (194.88 GiB 209.25 GB)
    md60 Array Size : 204343296 (194.88 GiB 209.25 GB)
    so that looks like md60 is 2MB bigger than md6 (which is how I set it up), so how can it be too small?

    What am I missing here?

    Any advice gratefully received?

    Nick(c)

  2. #2
    Join Date
    Nov 2009
    Location
    West Virginia Sector 13
    Posts
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    Default Re: mdadm partiton not large enough to join array

    Not sure what you want to accomplish?

    RAID is not backup. At most it guards against a single drive failure.

    You also seem to have chosen a very complex setup.

    If you must have 100% reliable RAID use true hardware RAID and stay away from FAKE RAID.

    In my opinion RAID has a use in high demand 5 9s environments I see it as an obstical in less demanding ares such as typical desktop.

    Maybe you should look at BTRFS file system and it's snapshot feature

    Sorry I can't help with the oddball RAID setup.

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