As a GlusterFS developer, and furthermore the founder of a project to create a "cloud" version of GlusterFS aimed at exactly this use case, this is pretty darn interesting to me. I guess I'm supposed to pick away at all the feature differences between EFS and GlusterFS-on-EC2, or something like that, but for now I'm more pleased to see that this use case is finally being addressed and the solution seems well integrated with other Amazon features. Kudos to the EFS team.