added REX-Ray as volume plugin to plugin docs
@@ -44,6 +44,10 @@ The following plugins exist:
a plugin that provides credentials and secret management using Keywhiz as
a central repository.
+* The [REX-Ray plugin](https://github.com/emccode/rexraycli) is a volume plugin
+ which is written in Go and provides advanced storage functionality for many
+ platforms including EC2, OpenStack, XtremIO, and ScaleIO.
+
## Troubleshooting a plugin
If you are having problems with Docker after loading a plugin, ask the authors
