I was playing around with Rexray (v0.3.3 since v0.4 is not supporting EBS yet) and Docker and when starting a docker container I always got an error message like

docker: Error response from daemon: Container command 'XXXXXXX' not found or does not exist..

After trying to nail this problem down, I have a feeling that docker tries to access the rexray volume before it's fully mounted. It's also interesting that this is only a problem in docker >= v.1.11, after downgrading to docker v1.10.3 it's working as expected.