[tom910]

I think lees. Why AWS need to store 3 times if they can use Reed-Solomon algorithms (or similar) and decrease this number to 2 or 1.5 and save a lot of storage space

[Kluggy]

Reed-Solomon would allow you to lose any one of the three and recover. Losing two would be catastrophic.

AWS's guarantee is that you can lose two of the three copies and still have all the data. You can't do that without three complete copies.