After insatlling Dell (md3000) mutipath driver on your system, u see the devices. In my example i am able to see 6 dirve (800 + 400 + 400 ) GB each.
Now follows the below steps to create software raid.
1) Check mdamd command if not found then install through #yum install mdadm
2) command to create raid.
i) mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sde
ii) mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sdc /dev/sdf
iii) mdadm --create --verbose /dev/md2 --level=1 --raid-devices=2 /dev/sdd /dev/sdg
3) Check the status
# cat /proc/mdstat Personalities : [raid1]
md2 : active raid1 sdd[0] sdg[1]
439023552 blocks [2/2] [UU]
[=>...................] resync = 9.4% (41593920/439023552) finish=256.7min speed=25800K/sec
md1 : active raid1 sdc[0] sdf[1]
439023552 blocks [2/2] [UU]
[==>..................] resync = 11.1% (48802368/439023552) finish=222.3min speed=29248K/sec
md0 : active raid1 sdb[0] sde[1]
878047168 blocks [2/2] [UU]
[=>...................] resync = 8.1% (71613248/878047168) finish=299.9min speed=44808K/sec
or use this command.
#mdadm --detail /dev/md0
4)Now create mdadm.conf configuration file.
#mdadm --detail --scan --verbose
#mdadm --detail --scan --verbose > /etc/mdadm.conf
#cat /etc/mdadm.conf
ARRAY /dev/md0 level=raid1 num-devices=2 metadata=0.90 UUID=2a3991ba:39a6377a:dd723100:e68056a3
devices=/dev/sdb,/dev/sde
ARRAY /dev/md1 level=raid1 num-devices=2 metadata=0.90 UUID=4f1ebc35:a3e06fe2:55e28aa2:1b96898f
devices=/dev/sdc,/dev/sdf
ARRAY /dev/md2 level=raid1 num-devices=2 metadata=0.90 UUID=78f8c8ba:a3ed13e1:a3b78f6d:79719608
devices=/dev/sdd,/dev/sdg
***added this line on top DEVICE /dev/sdb /dev/sde /dev/sdc /dev/sdf /dev/sdd /dev/sdg :in our env may be not required for any one****
5) Now you can run fdisk to show the status.
#fdisk -l
Disk /dev/md0: 899.1 GB, 899120300032 bytes
2 heads, 4 sectors/track, 219511792 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk /dev/md0 doesn't contain a valid partition table
Disk /dev/md1: 449.5 GB, 449560117248 bytes
2 heads, 4 sectors/track, 109755888 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk /dev/md1 doesn't contain a valid partition table
Disk /dev/md2: 449.5 GB, 449560117248 bytes
2 heads, 4 sectors/track, 109755888 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
6)Now format your raid device & add entry in fstab.
some useful command.
#mdadm --assemble --scan
Enjoy
Now follows the below steps to create software raid.
1) Check mdamd command if not found then install through #yum install mdadm
2) command to create raid.
i) mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sde
ii) mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sdc /dev/sdf
iii) mdadm --create --verbose /dev/md2 --level=1 --raid-devices=2 /dev/sdd /dev/sdg
3) Check the status
# cat /proc/mdstat Personalities : [raid1]
md2 : active raid1 sdd[0] sdg[1]
439023552 blocks [2/2] [UU]
[=>...................] resync = 9.4% (41593920/439023552) finish=256.7min speed=25800K/sec
md1 : active raid1 sdc[0] sdf[1]
439023552 blocks [2/2] [UU]
[==>..................] resync = 11.1% (48802368/439023552) finish=222.3min speed=29248K/sec
md0 : active raid1 sdb[0] sde[1]
878047168 blocks [2/2] [UU]
[=>...................] resync = 8.1% (71613248/878047168) finish=299.9min speed=44808K/sec
or use this command.
#mdadm --detail /dev/md0
4)Now create mdadm.conf configuration file.
#mdadm --detail --scan --verbose
#mdadm --detail --scan --verbose > /etc/mdadm.conf
#cat /etc/mdadm.conf
ARRAY /dev/md0 level=raid1 num-devices=2 metadata=0.90 UUID=2a3991ba:39a6377a:dd723100:e68056a3
devices=/dev/sdb,/dev/sde
ARRAY /dev/md1 level=raid1 num-devices=2 metadata=0.90 UUID=4f1ebc35:a3e06fe2:55e28aa2:1b96898f
devices=/dev/sdc,/dev/sdf
ARRAY /dev/md2 level=raid1 num-devices=2 metadata=0.90 UUID=78f8c8ba:a3ed13e1:a3b78f6d:79719608
devices=/dev/sdd,/dev/sdg
***added this line on top DEVICE /dev/sdb /dev/sde /dev/sdc /dev/sdf /dev/sdd /dev/sdg :in our env may be not required for any one****
5) Now you can run fdisk to show the status.
#fdisk -l
Disk /dev/md0: 899.1 GB, 899120300032 bytes
2 heads, 4 sectors/track, 219511792 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk /dev/md0 doesn't contain a valid partition table
Disk /dev/md1: 449.5 GB, 449560117248 bytes
2 heads, 4 sectors/track, 109755888 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk /dev/md1 doesn't contain a valid partition table
Disk /dev/md2: 449.5 GB, 449560117248 bytes
2 heads, 4 sectors/track, 109755888 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
6)Now format your raid device & add entry in fstab.
some useful command.
#mdadm --assemble --scan
Enjoy