I'm talking about here. It is a technique that was developed to provide speed, reliability, and increased storage capacity using multiple disks, rather than single disk solutions. RAID basically takes multiple hard drives and allows them to be used as one large hard drive with benefits depending on the scheme or level of RAID being used. Of course, the better the RAID implementation, the more expensive it's probably going to be. There is really no one best RAID implementation.
Some implementations are better than others depending on the actual application.
It used to be that RAID was only available in expensive server systems. However, with the advent of inexpensive RAID controllers, it seems it has pretty much reached the mainstream market. Performance nuts, such as myself, are always looking for the latest technology to give us that edge we need. Of course, the mainstream implementation has it's limitations, and RAID isn't really for everyone. There are many levels of RAID being used today.