Slow repair on empty cluster

Background: I have done:

• I've set up three (Datastax DSE) nodes with replication factor of 3. Each node has 256 vnodes. Each is running Cassandra 2.0.8.39, according to `cqlsh`.
• enabled authorization
• enabled authentication
• created a custom keyspace with replication factor and created a smaller table without putting any data into it.

For fun execute a `nodetool repair` in my terminal this takes 23 minutes. This feels a bit slow to me for not having put any data into my cluster. Is this expected? Or a bug?