Once the cluster is established, StorageOS creates a default storage pool from all the nodes in the cluster:

storageos pool ls --format "table {{.Name}}\t{{.Nodes}}\t{{.Total}}"

Each node contributes about 15GB to the pool, so the pool has 45GB of total capacity.

You can see more detail about the pool by inspecting the JSON configuration:

storageos pool inspect default

The storage pool contains host01, host02 and host03 under controllerNames.

Applications can create a StorageOS volume through the CLI, API or GUI. Try creating a volume:

storageos volume create myvol

Since we didn't specify any specific size or storage features for the new volume, StorageOS uses the default settings. Let's find out what these settings are:

storageos volume ls --format "table {{.Name}}\t{{.Size}}\t{{.Location}}"

NAMESPACE/NAME: Namespaces help different projects or teams share a StorageOS cluster. Note that default refers to the default namespace that StorageOS created for myvol, rather than the default pool.

SIZE: The default volume size is 5GB.

LOCATION: The host that StorageOS provisioned the volume on.

StorageOS volumes are thin provisioned, so storage is dynamically allocated to volumes as it is used. You can even provision volumes that are larger than the storage pool; try resizing the volume to 100GB:

storageos volume update --size 100 default/myvol

Inspect the volume to check the size was updated in the JSON config:

storageos volume inspect default/myvol

To use StorageOS volumes with containers, you use the standard Docker run command with some additional flags. Let's run a container with a shell so we can run commands inside the container:

docker run -it --volume-driver storageos --volume myvol:/data busybox sh

--volume-driver storageos tells Docker that StorageOS is managing these volumes.

--volume myvol:/data instructs Docker to mount myvol to /data inside the container.

If you run ls /data you should see lost+found, because StorageOS volumes are automatically formatted with a filesystem on creation. Try writing data into a file:

echo "I'm writing some data to a StorageOS volume" > /data/myfile

Exit the shell and the container:

exit

Check that the data was persisted by mounting the volume on the host and reading the file:

storageos volume mount default/myvol /mnt

ls /mnt

cat /mnt/myfile

You should see the string you just wrote: I'm writing some data to a StorageOS volume.

Now unmount the volume again:

storageos volume unmount default/myvol

StorageOS volumes are globally namespaced, meaning that any host can access the volumes.

Switch to the second host and mount myvol again:

docker run -it --volume-driver storageos --volume myvol:/data busybox sh

Check the container can see myfile: cat /data/myfile