Hhow data is accessed by Brisk?

[Cassa L]

I have a very basic question related to brisk as I am trying to
understand how data is queried in Brisk architecture.

As the DataStax Enterprise White paper says -
"app data and analytics both take place in the same distributed
system, but users have the flexible ability to assign resources so
that analytical work doesn’t slow down real-time processing.
Users simply define one or more replica groups, and configure the role
of each group – one or more Cassandra, Hadoop or HDFS (i.e., HDFS
without job/task tracker) nodes. Writes are instantly replicated
between the replica groups."

So if I create external table in Hive and run query against it ,
does that mean that data query will only occur on Brisk nodes and not
on Cassandra nod? . If so, is this true for mixed node cluster as well
as multi-dc setup ? When external table is created, Does the Brisk
node keep copy of data in cfs ?

Thanks,
L