I didn't say that RAID5 and RAID10 are similar in terms of reliability (most of my comment said that RAID10 had many upsides over RAID5 in terms of reliability). I said they you should consider them to have the same level of redundancy -- unless you like to play Russian roulette with your data. Yeah, if you have more drives there are less bullets in the revolver but I'd prefer to not play that game in the first place. If you need a system that can survive 2 independent disk failures, use 3-way mirrors.