RAID: A Guide For All ... Part 1

The use of RAID, a Redundant Array of Inexpensive Disks, up until a few years ago was pretty much limited to servers and high end workstations; this was primarily due to the cost of the controller and the accompanying hard drives. Today that's not at all the case! Most of the newer motherboards provide one or more onboard RAID controllers capable of delivering configurations up to and including RAID 5. With the cost of disk storage at an all time low the two primary barriers to using this once esoteric form of data storage have been lifted.

Let me state for the record that I know there are a number of quality guides on the Internet covering this subject. My rationale for writing this guide is quite simple, the most recent guide(s) I was able to find was written in 2004, the only exception to this was a white paper article published by California Software Labs in February, 2006. Even though a great deal of the techniques for RAID implementation haven't changed, much of the equipment has. In 2004 onboard RAID controllers were just beginning to appear, today they're commonplace and considerably better. In 2004 SATA drives were not the standard as they are today.

My goal is to give our readers from beginner to expert a guide that will benefit them. The beginning users should come away with an understanding of all the intricacies of RAID enabling them to make an informed decision whether RAID is an appropriate modality for their use. The more advanced users should garner additional information helping them decide if moving to a different level of RAID in hopes of reaching some predetermined level of performance or redundant protection is feasible. Most important of all, I want this to be a positive learning experience for both you and me!

Rather than than trying to fix something that's not broken, I plan through research to take what has already been written, coupled with my own thoughts and experiences and update it to a very thorough, yet easy to read guide to RAID that's applicable to 2006. Initially I plan for the guide to have two parts. Part 1, will be function and procedure oriented covering the basics of RAID including the history, terminology, types of RAID, functionality, pros and cons, and descriptions. Part 2, will be dedicated solely equipment ranging from on-board chip sets to separate, highly efficient RAID cards for your project ranging from the more cost efficient approach up to unlimited approach. Emphasis here will be limited to a single system and small home networks as larger, enterprise wide networks will exceed the scope of most of our readers.

Most credit the beginning of RAID research to Norman Ken Ouchi at IBM. He was issued U.S. Patent 4,092,732 titled "System for recovering data stored in failed memory unit" in 1978 and the claims for this patent describe what would later be termed RAID 5 with full stripe writes. This 1978 patent also mentions that disk mirroring or duplexing (what would later be termed RAID 1) and protection with dedicated parity (what would later be termed RAID 4) were prior art at that time.

RAID levels 1 through 5 were formally defined by David A. Patterson, Garth A. Gibson and Randy H. Katz in the paper, "A Case for Redundant Arrays of Inexpensive Disks (RAID)". This paper also listed a mathematical calculation that many believe is still accurate today which is used to determine Meant Time To Failure (MTTF), a key factor in a systems's fault tolerance. While there have been many ground breaking advances in RAID development since this article, one must fully credit these researchers form the University of California at Berkeley as having the paternity rights to what is considered modern day RAID.

While this history is extremely meaningful to the development of modern day RAID, it did not stop there. Annually the RAID Symposia, an international conference which began in 1998 on RAID development is held. Here researchers, developers, and other interested parties from all over the world meet to present and discuss key research oriented information that is instrumental to the continuing development of even more efficient RAID hardware and software for the present and future.