[drvdevd]

And I've actually had (a couple times now) random hardware failings, with random notification emails from Amazon, on EBS storage on AWS, with accompanying data loss.

Might as well treat your zpool like it's on real hardware and configure raidz accordingly. The cloud does have real, problematic hardware behind it, and it's important to remember that.

[edit] especially if you can configure your block devices such that you know they're sitting on different physical hardware at the cloud data center, you will gain that benefit of ZFS