I'm looking to deploy servers by building images which I then use to create identical copies of servers. I also want to mount a separate disk that persists over rebuilding a server. On EC2, I would do this by having an ephemeral root filesystem and an EBS volume mounted at /var/lib/mysql, for example. But EBS is really slow. What would be brilliant is if I could in essence have two local disks – one which is the root filesystem and can be rebuilt from images, and another that persists over the reimage and can be mounted again in the same place. See also: http://martinfowler.com/bliki/ImmutableServer.html