How to create a Raid Device using Madadm

http://helpinlinux.blogspot.com/search/label/storage

How to create a Raid Device using madadm in linux rhel5

with level 5, 0 and 1

The following article explains what is Raid, what are important levels and how to install and

configure a raid device in a linux system using the software mdadm. This is tested in Redhat

rhel5 and also works with other distributions as fedora, centos etc.

What is RAID?

RAID is redundant array of independent or inexpensive disks. It is mainly used for data

protection. It protects our data storage from failures and data loss. All storage units now use

raid technology.

It has following uses.

1. Data protection

2. Increasing performance

Types of RAIDs:

There are alot of levels of RAIDs. But the main levels are

1. Level 0 or Striping

2. Level 1 or Mirroring

3. Level 5 or Striping + Parity

Level 0:

It is also known as striping. You know hard disk is a block device. Datas are read and written

from/to it by blocks.

Suppose we have data block as below

1 0 1 1

Suppose each bit takes one cpu clock cycles for writing into a disk. Total, it will take 4 cpu

clock cycles.

With stripping:

In striping we use "N" number of hard disks. RAID devides the data block by "N" and writes

each part to each disk in parallel.