Abstract
In 2016, CERN decided to phase out the legacy OpenAFS storage service due to concerns for the upstream project’s longevity, and the potential impact of disorderly service stop on CERN’s computing services. Early 2019, the OpenAFS risks of the project collapsing have been reassessed and several early concerns have been allayed. In this paper we recap the work done so far, highlight some of the issues encountered, and present current state and planning.
Highlights
AFS [1] is a shared secure filesystem with global namespace, and OpenAFS [2] is its major implementation
That decision was taken due to a high perceived risk of a fast upstream project collapse at an inconvenient moment, i.e with CERN still heavily relying on AFS in the middle of a Large Hadron Collider (LHC) run
An investigation showed that ROOT data files made for 47% of the data volume found there, in particular by users from the two largest LHC experiments at CERN
Summary
AFS [1] is a shared secure filesystem with global namespace, and OpenAFS [2] is its major implementation. Instead, based on the various use cases, the data was to migrate to a set of different services (or, in some case, to be deleted). In case where this was not straightforward, these other services would have to be adapted, and the migration might require user-side changes to their workflows. The CERN AFS space was split into different areas: personal storage space (separate homedirectories and workspaces) and shared storage for projects or experiments (with delegated quota and volume administration). The major migration options initially foreseen for the AFS phaseout were CASTOR for archiving stale (but important) data, CVMFS for (large-scale) software distribution, EOS [4] for data that needed to be kept accessible, and deletion, for clearly-identified obsolete content. We will compare the original phaseout planning with reality, highlight some of the issues encountered and the in-depth investigations triggered by the phaseout, summarize the current state of AFS at CERN and provide a brief outlook
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