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Old 03-17-2010, 06:06 PM   #1
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Registered: May 2004
Location: Orlando, FL
Distribution: Arch
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Software RAID1 Failure

Last night I had a 'software RAID1' mirror break. In short, /dev/sdb has failed and the drive has been replaced since then. My mirror (/dev/md0) was comprised of /dev/sda2 /dev/sdb2.

My system is up and running right now:

        Version : 0.90
  Creation Time : Thu Jan 14 06:02:07 2010
     Raid Level : raid1
     Array Size : 728571776 (694.82 GiB 746.06 GB)
  Used Dev Size : 728571776 (694.82 GiB 746.06 GB)
   Raid Devices : 2
  Total Devices : 1
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Wed Mar 17 19:02:30 2010
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           UUID : 628ada8a:a688bad8:5b69a113:4ec4a0dc
         Events : 0.28149

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       1       0        0        1      removed
My question is how can I re-join /dev/sdb2 in /dev/md0? I have searched Google and the 'mdadm' man page and can't seem to understand how to repair this broken mirror.
Old 03-17-2010, 06:24 PM   #2
Registered: Feb 2010
Distribution: gentoo, arch, fedora, freebsd
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mdadm /dev/md0 -a /dev/sdb2
Old 03-17-2010, 07:13 PM   #3
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That worked.
Old 03-23-2010, 02:18 PM   #4
Registered: Feb 2007
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In general the same "fix" works in any degraded RAID array (except 0, which isn't really RAID). Simply add the new/fixed partition back into the array.

It will take some to re-sync during which time the array is still available but you won't have redundency.


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