Software RAID in Red Hat Linux

To create a linear RAID array:

# mdadm --create --verbose /dev/md0 --level=linear --raid-devices=2 /dev/sdb /dev/sdc
# mdadm --detail --brief /dev/md0 >> /etc/mdadm.conf


To create a striped RAID array (RAID-0):

# mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sdb /dev/sdc
# mdadm --detail --brief /dev/md0 >> /etc/mdadm.conf


To create a mirrored RAID array (RAID-1):

# mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc
# mdadm --detail --brief /dev/md0 >> /etc/mdadm.conf


To start a RAID Array:

# mdadm --assemble /dev/md0 /dev/sdb /dev/sdc /dev/sdd

                                                    OR

# mdadm --scan --assemble --uuid=a26bf396:31389f83:0df1722d:f404fe4c


To list all software raid arrays and their component devices:

# cat /proc/mdstat
Personalities : [linear]
md0 : active linear sdd[0]
      10485752 blocks super 1.2 0k rounding

md1 : active linear sde[0]
      52428792 blocks super 1.2 0k rounding

unused devices:




 
To query a software raid array :

# mdadm --query /dev/md1
/dev/md1: 129.100GiB linear 1 devices, 0 spares. Use mdadm --detail for more detail.


To list details of a RAID array:

# mdadm --detail /dev/md1
/dev/md1:
        Version : 1.2
  Creation Time : Thu Dec 11 09:32:37 2011
     Raid Level : linear
     Array Size : 52428792 (50.00 GiB 53.69 GB)
   Raid Devices : 1
  Total Devices : 1
    Persistence : Superblock is persistent

    Update Time : Thu Dec 11 09:32:37 2011
          State : clean
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

       Rounding : 0K

           Name : server123:1  (local to host server123)
           UUID : c5804771:253326af:e062f685:cab35fed
         Events : 0

    Number   Major   Minor   RaidDevice State
       0       8       32        0      active sync   /dev/sdc


To examine a RAID array:

# mdadm --examine /dev/md0


To add a raid disk device and extend a linear software raid array :

# mdadm --detail /dev/md3 | tail -n 3
    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sdc
       1       8       17        1      active sync   /dev/sdd

# mdadm --grow /dev/md3 --add /dev/sde


To remove a RAID array:

# mdadm --stop /dev/md3
# mdadm --remove /dev/md3
# mdadm --zero-superblock /dev/sdc /dev/sdd