HDFS is a Java-based file system that provides scalable and reliable data storage, and it was designed to span large clusters of commodity servers. HDFS has demonstrated production scalability of up to 200 PB of storage and a single cluster of 4500 servers, supporting close to a billion files and blocks.
Google Spanner is a Google Cloud-based database system that is ACID compliant, horizontally scalable, and global. Spanner is the database that underpins much of Google’s own data collection, and it has been designed to offer the consistency of a relational database along with the freedom of a non-relational one.