RAID 1 is usually implemented as mirroring; a drive has its data duplicated on two different drives using either a hardware RAID controller or software (generally via the operating system). If either drive fails, the other continues to function as a single drive until the failed drive is replaced.

Software RAID under Linux is a rock solid solution for building RAID arrays at no cost. I personnally never had problems with software raid under Linux while i've seen expensive hardware RAID card failing and corrupting arrays. It's a little slower that hardware RAID but it remove a possible point of failure in a system and again, it's free.

I decided to buy two 80Gb drives and configure them in RAID-1. RAID-1 gives you mirroring and only requires two drives. RAID-5, for example, requires at least three. Now, I haven’t configured a RAID system for a while (five years?) and I was surprised at how easy Linux makes it.

RAID stand for a redundant array of inexpensive disks, a way of combining multiple disk drives into a single entity to improve performance and/or reliability. There are a variety of different types and implementations of RAID, each with its own advantages and disadvantages.

It is well known that the so-called "solid-state disks" (SSD) have very low access times. I could have tried to buy an SSD, but being a tinkerer, I decided for another option. Thumb drives / flash drives / pen drives are also a kind of SSDs, one could say - but they have lousy transfer rates. In the end, I decided to create a software RAID using four 2GB USB drives.

RAID controllers designed for hard disks and IOPS aren't going to cut it in the new world of solid state drives (SSDs) and pNFS, which are capable of feeding so much more data into the channel that streaming bandwidth is going to become the problem for RAID vendors.

This short guide explains how you can configure software RAID to send you an email when something's wrong with RAID, for example if a hard drive fails. I've tested this on Debian Etch, but it should apply to all other distributions with minor adjustments to paths, etc.

This is an example of productive and practical use of a RAID. Granted, this project does not have the archaic grandeur of a Floppy Disk RAID, but then again, the capacity and performance of this system are utterly superior to those of a Floppy Disk RAID

Want to get an idea of what speed advantage adding an expensive hardware RAID card to your new server is likely to give you? You can benchmark the performance difference between running a RAID using the Linux kernel software RAID and a hardware RAID card. My own tests of the two alternatives yielded some interesting results.