The Cassandra Data Migrator (CDM) is a tool used to move data between Apache Cassandra and DataStax Astra DB, it works with the Apache Spark framework to transfer large amounts of data without intermediate storage. The CDM can be run as a Docker container or built from its JAR file, it requires configuration through the `cdm.properties` file specifying connection details, keyspace, table names, and migration settings. In contrast, the DataStax Bulk Loader (DSBulk) is a versatile tool that can work with any database operating on the CQL protocol standard, including Cassandra, and provides functionality for exporting, importing, and counting rows in Cassandra tables. DSBulk can be configured through command line flags and has been used successfully in many Cassandra migrations, but may introduce load onto the origin Cassandra cluster during export operations. Both tools have their strengths and weaknesses, and it is recommended to assess the cluster's resources before migration to minimize impact on production usage.