- Hadoop is an ecosystem, not a single product.
- HDFS is a file system, not a DBMS.
- MapReduce provides control for analytics, not analytics per se.
- Hive resembles SQL, but is not standard SQL.
- Hadoop is about data diversity, not just data volume.
- Hadoop is a complement of BI and DW—rarely a replacement.
- Hadoop enables many types of Analytics, not just Web Analytics.
These points are from TDWI report.