1. Apache cassandra (2020). https://cassandra.apache.org/
2. Apache hbase (2020). https://hbase.apache.org/
3. Apache hdfs (2020). https://hadoop.apache.org/docs/r1.2.1/hdfs_design.html
4. Kairosdb (2020). https://kairosdb.github.io/
5. Opentsdb (2020). http://opentsdb.net/