ALICE (A Large Ion Collider Experiment) is a general purpose, heavy ion collision detector at the CERN LHC. It is designed to study the physics of strongly interacting matter, and in particular the properties of Quark-Gluon Plasma (QGP), using proton-proton, nucleus-nucleus and proton-nucleus collisions at high energies. The ALICE experiment will be upgraded during the Long Shutdown 2 (LS2, 2020-2021) in order to exploit the full scientific potential of the future LHC. Such upgrade will pose the challenge the challenge of reading out and inspecting the Pb–Pb collisions at rates of 50 kHz, sampling the pp and p–Pb at up to 200 kHz. The resulting data throughput from the detector has been estimated to be greater than 3.4 TB/s for Pb–Pb events, roughly two orders of magnitude more than in Run 2.
To be able to cope with this amount of data, and to be able to store it, we need to compress it intelligently by running the events reconstruction mostly online. The goal is to store 90GB/s, and thus to achieve a compression factor of more than 30.
The O² software framework will provide the necessary abstraction so that common code can deliver the selected functionality on different platforms. The framework will also support a concurrent computing model for a wide spectrum of computing facilities, ranging from laptops to the complete O² system. Off-the-shelf open source software conforming to open standards will be used as much as possible, either for the development tools or as a basis for the framework itself.