RAID's Days May Be Numbered
Is RAID Necessary Anymore?
The concept of parity-based RAID (levels 3, 5 and 6) is now pretty old in technological terms, and the technology's limitations will become pretty clear in the not-too-distant future - and are probably obvious to some users already. In my opinion, RAID-6 is a reliability Band Aid for RAID-5, and going from one parity drive to two is simply delaying the inevitable.
We'll start with a short history of RAID, or at least the last 15 years of it, and then discuss the problems in greater detail and offer some possible solutions.
Some of the first RAID systems I worked on used RAID-5 and 4GB drives. These drives ran at a peak of 9 MB/sec. This, of course, was not the first RAID system, but 1994 is a good baseline year. You'll need to click on the image below for how the RAID rebuild picture has changed in the last 15 years.