Linux Software RAID - A Belt and a Pair of Suspenders

Linux comes with software-based RAID that can be used to provide either a performance boost or add a degree of data protection.

This tutorial is an excellent about LINUX RIAD software which described the method for the various tasks. It gives a quick introduction to Linux software RAID and walks through how to create a simple RAID-1 array.
Details:
http://www.linux-mag.com/cache/7475/1.html