According to this link: http://aws.amazon.com/ebs/details/#availabilityanddurability
It said:
Amazon EBS Snapshot can expect an annual failure rate (AFR) of between 0.1% – 0.5%, where failure refers to a complete loss of the volume. This compares with commodity hard disks that typically fail with an AFR of around 4%,
Assume AFR of a commodity disk a 4%, and if I use RAID 1, chance of losing a volume is 4% * 4% = 0.16%, so on average EBS is worst that a Raid 1 configuration of commodity hard disks right?