Support for mounting external volume to containers

[dcvan24]

Marathon supports mounting external volumes to containers but it is still in beta. The driver used for the volume mounting in DC/OS is Rex-Ray. It requires for further investigation to find out how to integrate this functionality into PIVOT, in order to handle shared file systems such as NFS, WebDAV among others.

[dcvan24]

Just got Rex-Ray running and successfully mounted volumes in AWS EBS/S3/GCE Persistent Disk (PD) to Docker containers. Rex-Ray has developed Docker plugins compliant to Container Storage Interface (CSI) for mounting external volumes, which makes the volume mounting more convenient.

However, there are some limitations on different types of volumes, most of which are imposed by the storage providers:

1. AWS EBS and GCE PD are limited to being mounted to VM instances running on AWS and GCE correspondingly, but cannot be mounted to any VM running elsewhere.

2. S3 can be mounted to any VM regardless of where the VM is provisioned.

3. It is still unclear to me how to use the Docker plugin for GCE PD. The example in the official docs does not work.

4. Rex-Ray does not support Google Cloud Storage yet.

In summary, Rex-Ray has a better support for AWS than GCE. It is great that S3 buckets can be mounted anywhere. I will try AWS EFS and other on-premise storage systems recently.