It was designed as an alternative to the Apache Hadoop Distributed File System (HDFS), intended to deliver better performance and cost-efficiency for large-scale processing clusters.
It has three components: In a cluster of hundreds or thousands of machines, the odds are low that all will be running and reachable at any given moment, so fault tolerance is the central design challenge.
QFS is written in the programming language C++, operates within a fixed memory footprint, and uses direct input and output (I/O).
QFS evolved from the Kosmos File System (KFS), an open source project started by Kosmix in 2005.
Quantcast adopted KFS in 2007, built its own improvements on it over the next several years, and released QFS 1.0 as an open source project in September, 2012.