Spark2.x comes bundled with its own scala (version 2.11). You do NOT need to install scala 2.11 separately or upgrade your existing scala 2.10 version. The Spark 2 installation will take care of the scala version for you. Once you install Spark2 (just ensure to review the pre-requisites and known issues.) you can find Scala 2.11 libraries under /opt/cloudera/parcels/SPARK2/lib/spark2/jars
# ls -l /opt/cloudera/parcels/SPARK2/lib/spark2/jars/scala*
-rw-r--r-- 1 root root 15487351 Jul 12 19:16 /opt/cloudera/parcels/SPARK2/lib/spark2/jars/scala-compiler-2.11.8.jar
-rw-r--r-- 1 root root 5744974 Jul 12 19:16 /opt/cloudera/parcels/SPARK2/lib/spark2/jars/scala-library-2.11.8.jar
-rw-r--r-- 1 root root 423753 Jul 12 19:16 /opt/cloudera/parcels/SPARK2/lib/spark2/jars/scala-parser-combinators_2.11-1.0.4.jar
-rw-r--r-- 1 root root 4573750 Jul 12 19:16 /opt/cloudera/parcels/SPARK2/lib/spark2/jars/scala-reflect-2.11.8.jar
-rw-r--r-- 1 root root 648678 Jul 12 19:16 /opt/cloudera/parcels/SPARK2/lib/spark2/jars/scala-xml_2.11-1.0.2.jar
-rw-r--r-- 1 root root 802818 Jul 12 19:16 /opt/cloudera/parcels/SPARK2/lib/spark2/jars/scalap-2.11.8.jar
The reason both Spark1.6 and Spark2.x can coexist is attributed to them having separate parcels and have separate ways of calling. Example to run an application with Spark2, you need to use spark2-shell, spark2-submit, or pyspark2. Likewise, if you want to run an application using Spark1.6 (CDH bundled), you need to use spark-shell, spark-submit, or pyspark.