Help in need: mdadm and software RAID5 recovery on FC4

[Justin Piszcz]

On Fri, 25 Aug 2006, Robinson Tiemuqinke wrote:

> Hi,
>
> I still have several Fedora Core 4 boxes running with
> software RAID5 created with mdadm tool.
>
> Now one underlying component disk failed and have to
> be replaced. But I have to save the data on the
> software RAID5 device.
>
> Any one can show me the correct "official way" to do
> this job? Thanks a lot.
>
> Detailed background: the RAID5 was created with the
> following command:
>
> " mdadm --create /dev/md0 --level=5 --raid-devices=3
> /dev/sd[bcd]1 "
>
> and now the sdb1 failed and I will replace it soon.
>
>  Please help.
>
> --Robinson
>
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Like so:


p500b1:~# mdadm -D /dev/md0
/dev/md0:
         Version : 00.90.03
   Creation Time : Sat May 27 15:38:10 2006
      Raid Level : raid5
      Array Size : 4417280 (4.21 GiB 4.52 GB)
     Device Size : 2208640 (2.11 GiB 2.26 GB)
    Raid Devices : 3
   Total Devices : 2
Preferred Minor : 0
     Persistence : Superblock is persistent

     Update Time : Sat May 27 16:20:54 2006
           State : clean, degraded
  Active Devices : 2
Working Devices : 2
  Failed Devices : 0
   Spare Devices : 0

          Layout : left-symmetric
      Chunk Size : 64K

            UUID : a6a0f4cc:4311f7d2:739fc939:64a49b1c
          Events : 0.853

     Number   Major   Minor   RaidDevice State
        0       8        1        0      active sync   /dev/sda1
        1       8       17        1      active sync   /dev/sdb1
        2       0        0        -      removed

------

p500b1:~# mdadm /dev/md0 -a /dev/sdc1
mdadm: hot added /dev/sdc1
p500b1:~#


p500b1:~# mdadm -D /dev/md0 |grep Rebuild
  Rebuild Status : 4% complete
p500b1:~#

p500b1:~# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid5] [raid4] [raid6]
md0 : active raid5 sdc1[3] sdb1[1] sda1[0]
       4417280 blocks level 5, 64k chunk, algorithm 2 [3/2] [UU_]
       [======>..............]  recovery = 32.7% (724864/2208640) 
finish=5.3min speed=4588K/sec

unused devices: <none>
p500b1:~#

---------

recovery complete

p500b1:~# mdadm -D /dev/md0
/dev/md0:
         Version : 00.90.03
   Creation Time : Sat May 27 15:38:10 2006
      Raid Level : raid5
      Array Size : 4417280 (4.21 GiB 4.52 GB)
     Device Size : 2208640 (2.11 GiB 2.26 GB)
    Raid Devices : 3
   Total Devices : 3
Preferred Minor : 0
     Persistence : Superblock is persistent

     Update Time : Sat May 27 16:33:51 2006
           State : clean
  Active Devices : 3
Working Devices : 3
  Failed Devices : 0
   Spare Devices : 0

          Layout : left-symmetric
      Chunk Size : 64K

            UUID : a6a0f4cc:4311f7d2:739fc939:64a49b1c
          Events : 0.859

     Number   Major   Minor   RaidDevice State
        0       8        1        0      active sync   /dev/sda1
        1       8       17        1      active sync   /dev/sdb1
        2       8       33        2      active sync   /dev/sdc1
p500b1:~#