RAID

#fdisk /dev/sda

#create 3 partition (/dev/sda6 /dev/sda7 /dev/sda8) with space 100M the partition type should be “fd”

#init 6

#format the above created 3 partitions

#mdadm  --create  /dev/md0 --level=5 --raid-disk=3 /dev/sda6 /dev/sda7 /dev/sda8 {for create raid partition)

#mke2fs -j  /dev/md0

#mkdir /raid

#mount /dev/md0 /raid or use /etc/fstab for permanent mount

#mdadm --detail /dev/md0   - for verify all raid partition are working fine (u can use #cat /proc/mdstat also)

#cp some folder or files  to /raid

#Now assume that hard disk /dev/sda6 is failed

#mdadm /dev/md0 –fail /dev/sda6 – command to make the partition gets fail.

#mdadm --detail /dev/md0 – verify whether the /dev/sda6 has failed or not.

#mdamd /dev/md0 –remove /dev/sda6 – remove the faulty disk from raid (note u must to set fail status before removing the hard disk)

#mdadm /dev/md0 –add /dev/sda6 – to add the new partition in raid

How to remove the raid devices

#umount /raid

#mdadm –stop /dev/md0

#mdadm –remove /dev/md0

#remove entry from /etc/fstab 

#fdisk /dev/sda

#delete the partition /dev/sda6 /dev/sda7 /dev/sda8

In real time environment work

(***YOU MUST CREATE 3 PARTITION WITH 3 DIFFERENT HDD***) FOR RAID CREATTION.