If you like speed, but don't like spending money, software RAID 0 is for you!
Generally, RAID (Redundant Array of Inexpensive Disks) is found on expensive
corporate servers, where performance and reliability matter most. Such servers
generally use SCSI RAID cards that allow RAID modes 0-5 on SCSI disks.

For the home user, SCSI drives and SCSI RAID cards are often overkill, not to
mention very expensive. The alternative is IDE RAID, which requires either
an add-on RAID controller card (approx. $100 retail), or an integrated
motherboard RAID controller. The latter usually tends to be a form of software
RAID (that only works in Windows), not true hardware raid.

There are multiple modes of RAID, each with tradeoffs between speed and data
redundancy. The highest-performing mode is RAID 0, which evenly distributes disk
writes and reads across all member disks of the RAID array. While this mode
offers zero redundancy, it boosts the speed of two drives working together to
greatly outperform a single drive acting alone.

This tutorial will show you how to create a high-performance RAID-0 setup using
two IDE hard drives and NO hardware RAID controller. The Linux community has
created a form of software RAID that is available for free, and is not tied to any
specific vendor hardware. This should result in a huge jump in I/O performance
on your system.

The price of this performance boost is some additional CPU usage; however
most Gentoo systems are built on modern CPU's of a gigahertz or more,
which is more than enough power to drive the array without impacting system performance.

You'll need two IDE hard drives of equal (or almost equal) size. It does not
matter if the drives come from different hardware vendors, but they must be as
close to the same size as possible. (Note: if the size of each drive
differs substantially, the RAID array will shrink to be double the size of the
smallest drive in the array, regardless of whether one drive is larger.)

This document is meant to be used in tandem with the Gentoo Linux Installation
Instruction document. You will need to swap between that document and this one
during installation, paying attention to where the steps differ.
(Note: I owe a great deal of credit for this document to Chris Atwood,
whose RAID-1 directions got me started.)

This tutorial assumes you have both drives connected to your IDE controller. The
ideal setup for maximum performance is for each drive to be set as "master" and
connected to a separate IDE channel. If you have other devices (such as a CDROM)
as slave drives on the same channel, you may experience some performance degradation.

Let's walk through it:

1) Boot the Gentoo LiveCD.
2) Load the module for multi-device support:
# modprobe md
3) Configure networking
4) Set your system date/time.
5) Filesystems, partitions and block devices step:

Follow the Gentoo guidelines of creating /boot, swap, and / partitions, but
create IDENTICAL partitions of the SAME SIZE on BOTH drives. Each physical drive
should look identical to the other, in terms of partitioning. When choosing
the partition type, be certain to select type 83 Linux for the /boot partition.
DO NOT make it a RAID partition. Make the swap partition a type 82 swap, and
make the large / partition type FD (Linux RAID autodetect).

(Note: A software RAID array is not bootable, so you need to use a separate
/boot partition that is not part of the array)

6) Create an /etc/raidtab file. This file maps virtual RAID drives to physical
partitions, and is required for your array to function. If your drives are of
different sizes (which is not recommended), the smaller of the two drives should
be raid-disk 0 in this file.

# / partition
raiddev /dev/md0 # raid device name
raid-level 0 # raid 0
nr-raid-disks 2 # number of disks in the array
chunk-size 32 # stripe size in kilobytes
persistent-superblock 1
device /dev/hda3 # device that comprises the raid array
raid-disk 0 # disk positing index in array
device /dev/hdc