Hi
I've started the DS210: DataStax Enterprise 6 Operations course and downloaded both versions of Cassandra: DSE and regular one from Apache. Watching the topic "Configuring Clusters" I noticed num_token is 128 whereas if we look into cassandra.yaml of Apache its value is 256.
So, if I'm trying to pass the exam can this difference act on my exam ?
The "default" number of tokens depends on which distribution of Cassandra you're using and whether you're comparing what's in cassandra.yaml versus the defaults in the source code. Allow me to explain.
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;
The default cassandra.yaml that ships with DSE (for example, DSE 6.0) 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.
The latest version of the courses are using DSE 6.0 so the defaults above apply.
In the exam, the answer will depend on the question you are asked. For example, if the question is "what is the default value of num_tokens set in the cassandra.yaml of open-source Cassandra?", the answer is 256. Cheers!
Not a problem! Good luck with the exam if you're taking it. Cheers!
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