I tried to write a positive happy uplifting page about the glorious RAID provided with Linux but Google and a million Linux bigots defeated me so hear is a rant. Hopefully the new breed of Linux converts will heal the situation.
Search online for information about Linux RAID. You will get endless obsolete answers. Google does not help by placing pages from 2008 ahead of pages form today or by placing pages from 2002 ahead of pages from 2008. I am sure that if Google found a page from 1595, Google would place it ahead of the pages from 2002. A cave painting dated 25000 BC would rank first.
Google, when it comes to trying to use Linux instead of Windows, you are part of the problem, not the solution!
Search online for information about RAID stripe size or any other slightly technical question related to RAID. You will get endless unusable answers. The pages listed are mostly copies of other pages with not indication of which might be the original. Where there is a variation, it is mostly people asking the same question in a different forum in the hope of getting a usable answer but instead getting the same useless answer copied from somewhere else.
The current version of Ubuntu is 10.4.1, at the time of writing, but the answers are written for Ubuntu 8 or 6 or earlier. In an age of computer controlled fuel injection, the answers tell you how to stack wood in the fire box of a steam engine or how to put a harness on a horse. There is a real need for people who can produce documentation for the people trying to use Linux, not for the people who learned to use Unix back before Homo Erectus was born.
Hardware or software based RAID
Most of the recommendations are for hardware based RAID instead of software RAID. Hardware RAID requires very expensive hardware and the hardware is rarely faster than what you would achieve if you spent the same amount on improving the performance of your base computer. The hardware RAID device has to have a duplicate computer and duplicate memory. There was a time when the overhead of RAID was a significant load on a computer but not now.
As a kid back in the 1970s I built a PC using two processors so the second processor could perform RAID style disk operations. By the time I finished it, there was a new processor that was 40 percent faster and could hand the disk operations without a second processor. Memory was still tight but that was solved a year or two later later with a new generation of the Intel processor, the one that the Seattle Computer Products company used for QDOS, later sold by a company named Microsoft as MSDOS. Every time I added a second processor to a computer to improve disk operations, the computer increased in speed by more than the power of a second computer. Hardware RAID was never needed for processor speed.
The hardware device often cheats when reporting write speed by reporting the write completion before the write is completed. You then have to use additional hardware to ensure your computer keeps going after a power failure because the computer needs extra time to write the writes that are not really complete. Using hardware based RAID is often more dangerous than software based RAID if you do not know exactly how the hardware works.
The recommendations for hardware based RAID are irrelevant to software based RAID because the approach is totally different and depends entirely in the individual hardware used in the hardware RAID controller.
Hardware assisted RAID
There is a type of RAID where hardware assists software and it is also called
fake RAID because some people do not understand how it works or why it is used. Hardware assisted software RAID had a benefit for early computer processors before the processors had facilities to perform some special types of multiple byte operations. Now processors have the facility and the hardware assist is of no speed related benefit. In fact many of the hardware assist devices are actually slower.
The software drivers used to add the hardware assistance are still useful on Windows because Microsoft refuses to provide RAID on the desktop versions of Windows. Tens of millions of people suffer the results of Microsoft's stupidity coupled with a disk failure and many decide to convert to Linux as a result. If Microsoft refuses to let you take normal precautions against a disk failure and Linux gives to the protection for free, which operating system are you going to choose? For those not allowed to switch, using hardware assisted software RAID in Windows is a compromise.
Real software RAID is provided by Microsoft in the server editions of Windows and by Ubuntu in their server edition of Linux. In theory software RAID is available to all users of recent Linux version but, in practice, you often have to install separate software. Even if the software is is supplied as standard, there may not be a program provided to configure the RAID. You get really weird variations across Linux distributions.
Software RAID is really easy and safe and predictable in Windows, at least in the old server editions I used on many desktop computers when the Windows server edition was not much more expensive than the desktop version. For some reason Linux chooses to make it hard and unreliable. Or to be more exact, the people who choose what goes into a Linux distribution choose to copy the Microsoft limitation of RAID only for servers. Some distribution authors like to include everything then hide it. Weird. Weird. Weird.
Then the people writing Linux documentation choose to make the documentation really hard to follow by filling it with stupid statements and ancient DOS commands from the 1950s then the 1950s rubbish is repeated in the support forums Google chooses to list. The people writing in the support forums appear to compete to describe the most primitive practices. Google chooses to display documentation pages based on the most ancient and most obsolete first.
Linux will catch on big time when a modern species of humans build Linux distributions and write the documentation, assuming they do it before Linux is made obsolete by Android.