I did a search on redundancy and found several interesting threads (loved the one on small survival saws) but none really answered my question. I have been thinking about this (redundancy) a lot and how it relates to pack size and weight and how much gear any one person can carry. To clarify a little bit more I have some specific examples/questions as well.

For example, one thing I have been wondering about is signaling mirrors. I have a PSP with the 2 X 3 Resue Flash signal mirror in it. If I carry this in my pocket should I also carry a larger 3 X 5 signaling mirror in my pack? Should I carry another one somewhere else as well?

Here's another example. If I carry a PSK with three ways to make a fire, should I then carry additional fire-making gear in my pack as well? If yes, should it be duplicates of the same gear, something different, or both?

Do I carry a heatsheet in a pocket and a tarp in the pack? Cereal bars in my pocket and trail mix in the pack? I could go on and on with these kind of comparisons but I think everyone gets the point by now.

I have read several posts in other threads like "one is none, two is one and three is a backup," but when does enough become too much? As a final question, what items do you layer; items that redundancy is a must; and what items do you carry just one, the items you think redundancy is just not neccessary? Would you also relate how you layer them and the reasons why? The information would be greatly appreciated.