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kairosdb - Fast scalable time series database

OpenTSDB is a distributed, scalable Time Series Database (TSDB) written on top of HBase. OpenTSDB was written to address a common need: store, index and serve metrics collected from computer systems (network gear, operating systems, applications) at a large scale, and make this data easily accessible and graphable.

Axibase Time-Series Database (ATSD) is a next-generation statistics database. ATSD is for companies that need to extract value from large amounts of time-series data which exists in their IT and operational infrastructure. Built on top of Hadoop Distributed File System (HDFS), ATSD delivers scalability and performance beyond relational database limitations.

DalmatinerDB is a no fluff purpose built metric database. Not a layer put on top of a general purpose database or datastore.