I've been looking at my raid setups and I am beginning to really hate raid 1. During a drive failure, you don't know if the data on the other drive is correct or not. And what if one drive reads 1 and the other 0 without failure? How do you know which drive is correct?
Sure you could go with raid 6, but its a minimum of 4 drives. I think you can do the same with just 2 drives.
I've come up with a few raid levels, but why don't they exist?
- Raid on a single drive that also uses forward error correction like par2
- Like #1 but also mirrored (now you can ensure data is correct during failure)
This would require some custom hardware to perform the par2 calculation quickly. Also since its par2, for each drive you add to the array the par2 files can be smaller and smaller, since the amount of redundancy is the sum of the total size of the par2 files. See this to learn more about par2: http://www.quickpar.org.uk/AboutPAR2.htm