RAID

It is basicaly a file system use to manage data over multiple harddisk with and without backup depending upon the level of RAID (0,1,5)

The principle of raid is to use same make and model of harddisk.

How to create RAID ?

> first create three partitions

> then change TD from 83 to fd

> now create RAID by using these commands:

#mdadm -C /dev/md0 -l 5 -n 3 /dev/sda /dev/sdb /dev/sdc

> to check the details

#mdadm -D /dev/md0

> to watch online status of RAID

# watch cat /proc/mdstat

> now formatting the RAID partition

# mkfs.ext3 /dev/md0

> then make directory

# mkdir /dirname

> for permanent mounting add entry in fstab

# vim /etc/fstab
for eg. /dev/md0 /dirname ext3 defaults 0 0

# mount -a

> to show the RAID partition :

# df -TH

"FAULT TOLRENCE OF RAID"

> first to make faulty the partition

# mdadm /dev/md0 -f /dev/sdb ( this command is to use only to make faulty the partiton )

> then remove the faulty partition

# mdadm /dev/md0 -r /dev/sdb

> now create a new partition then add this partition on RAID

#mdadm /dev/md0 -a /dev/sdd