Volume problem

[dataanalyst]

I connected the container's data to a path on my HDD as described in the instruction:

$ docker run -d --name cass1 tobert/cassandra -v /srv/cassandra:/data;

Then, I connected to the container using the cqlsh and created a keyspace, a small table and filled it with some data.
$ docker exec -it cass1 cqlsh

I checked the /srv/cassandra on my HDD and no new file was generated.
Then, I stopped the cass1 container, removed it, created a new one (cass2)
docker run -d --name cass2 tobert/cassandra -v /srv/cassandra:/data;

When I connected to the second one ( docker exec -it cass12 cqlsh), no keyspace or data from the first one was preserved.
What am I doing wrong?