The HAMMER2 file system was conceived by Matthew Dillon, who initially planned to bring it up to minimal working state by July 2012 and ship the final version in 2013.[1][2] During Google Summer of Code 2013 Daniel Flores implemented compression in HAMMER2 using LZ4 and zlib algorithms.[3][4] On June 4, 2014, DragonFly 3.8.0 was released featuring support for HAMMER2, although the file system was said to be not ready for use.[5] On October 16, 2017, DragonFly 5.0 was released with bootable support for HAMMER2, though file-system status was marked as experimental.[6]
HAMMER2 had a long incubation and development period before it officially entered production in April 2018, as the recommended root filesystem in the Dragonfly BSD 5.2 release.[7]
Dillon continues to actively develop and maintain HAMMER2 as of June 2020.