question

I completely agree with you -- the question and the course content hasn't been clear about this.

The problem is that DS201 course question is referring to the num_tokens value configured in the DSE 6.0 cassandra.yaml. As Bettina already pointed out, I've previously explained it in question #4773. Allow me to explain.

Apache Cassandra

In open-source Cassandra, num_tokens is explicitly set to 256 in cassandra.yaml. This is true for both the latest C* 3.11.6 release and the current alpha release C* 4.0-alpha4:

num_tokens: 256

However if num_tokens is not set in cassandra.yaml, the number of tokens defaults to just 1 (see Config.java):

    public int num_tokens = 1;

DataStax Enterprise

The default cassandra.yaml that ships with DSE (for example, DSE 6.0 used in the DS201 course) has num_tokens set to 128 but it is commented out so it has no effect during bootstrap:

# num_tokens: 128

Unless num_tokens is explicitly set, a new node will bootstrap with just 1 token.

DS201 course

Specifically on your query about the Academy exercise on vnodes, the default value hasn't changed.

The quiz was asking about the default in the DSE 6.0.0 cassandra.yaml -- the version included in the VM image you downloaded for the course. And it was commented out with 128:

# num_tokens: 128

For the purposes of the DS201 course, 128 tokens is the answer. But I understand the confusion since if you install DSE without explicitly setting num_tokens, the node will bootstrap with just 1 token since the default configuration in DSE's Config.java is also 1 token:

    public int num_tokens = 1;

I've requested that the course be revised to avoid this confusion since it isn't really useful to someone who will eventually be a Cassandra administrator. Cheers!