WLCG — 1.5 EB, 170+ sites, 42 countries, 2M+ tasks/day

CERN's Worldwide LHC Computing Grid operates 1.5 exabytes across more than 170 sites in 42 countries and processes over 2 million tasks per day (S-0015).

The grid is a managed hierarchy with a central coordination layer at CERN, representing the most sophisticated Tier 2 system ever deployed. The 170+ participating sites are real failure-domain independence at large scale; the central coordination at CERN is the architectural risk (C-0012's structural dependency).

The case demonstrates two things: (1) Tier 2 architectures can scale to planetary distribution and exabyte storage, and (2) even at this scale, the coordination layer remains a single organizational dependency. The CERN-Russia/Belarus expulsion (E-0027) illustrates the latter — central coordination's terms of participation can change on geopolitical timelines that the participating institutions do not control.

WLCG is the high-water mark of Tier 2 in operational scale; it is also the upper bound on what Tier 2 can produce without the architectural shift to Tier 3.