I'd rather see it tried with ZFS and RAID-Z.

RAID-Z, among other things, is designed to offer parity (in a better implementation than traditional RAID parity). But you probably don't care about that with EBS. EBS volumes have an annual failure rate of 0.1%-0.5%. Commodity disks have an annual failure rate of 4%. That means that EBS is already taking care of parity in some way and you probably should worry about things other than that - like speed.

So, you could use RAID-Z to increase reliability (and it's a wonderful technology), but the speed of RAID-0 would be really nice for a good database server given that parity is taken care of.

Where did you get your annual failure rate data?

There's a section called "Amazon EBS Volume Durability" that goes over it. S3 is different from EBS. S3 is a lot more reliable. S3 is a spray files all over the place system like Danga's MogileFS. You simply save, say, 5 copies of a file on random servers and the likelihood that you're going to have data loss on all 5 of those servers before the system can replicate back up to having 5 copies of the file is next to nothing. Like, you loose two copies, but then the system creates two new copies on two other servers to get back up to 5 copies of the file.

EBS is less reliable. It's more like a RAID array. You can't really have a volume that spans different machines, nevermind a volume that spans data centers as S3 can. With EBS, a fire could just burn the disks an that would be the end of it (while, with S3, other data centers are unlikely to experience a similar fire in a short time frame). It's highly unlikely that EBS will fail on you - with an annual failure rate of 0.1%-0.5%, you shouldn't have to worry much.

So, EBS is a reliable storage system, but it isn't S3. Of course, S3 could never be fast like EBS. So, there is a trade off. Really, with EBS you can just snapshot it to S3 ever day and sleep soundly. In the highly unlikely event that you have a failure, you can restore without loosing more than 24 hours of data and the chance that you'll have to even do that is so low, but not as low as S3 where you can sleep completely soundly.