EOS (filesystem)

EOS (filesystem)
Name	EOS
Developer	CERN, European Organization for Nuclear Research
Introduced	2012
Latest release	2020s
Repo	GitLab
Written in	C++, Python
Operating system	Linux kernel
License	GPLv3

EOS (filesystem) is a distributed, low-latency storage system developed at European Organization for Nuclear Research for high-throughput scientific workloads. It provides object- and file-like interfaces optimized for large-scale physics experiments such as those conducted by ATLAS, CMS, and other collaborations on the Large Hadron Collider. EOS integrates with grid middleware, high-performance compute clusters, and archival systems managed by institutions like CERN and national laboratories.

Overview

EOS originated to meet the needs of data-intensive projects including Large Hadron Collider experiments, offering POSIX-like semantics combined with object-store scalability. It operates alongside systems such as dCache, XRootD, and Ceph, targeting workflows from reconstruction to analysis within federations like WLCG and collaborations with entities including Tier-0, Tier-1 data centers. EOS is maintained by teams at CERN IT and interacts with services used by European Grid Infrastructure members, FNAL, and academic partners.

Architecture and Design

EOS uses a modular architecture separating metadata services from data servers, similar in principle to designs seen in Google File System and Hadoop Distributed File System. The metadata layer is implemented with the concept of a namespace manager coordinating namespace shards, with influence from designs by Eric Brewer and concepts discussed at conferences such as USENIX. Data storage is organized into pools served by EOS disk servers and managed via a policy engine; agents interface with tape libraries like those from IBM for hierarchical storage management. Network protocols include native clients and integrations with HTTP, XRootD, and custom TCP-based protocols to serve different workload types.

Implementation and Features

EOS is implemented primarily in C++, with control tools in Python and administrative GUIs integrating with Grafana and Prometheus for observability used by operations teams. Features include namespace scalability through distributed namespace managers, snapshotting, replication policies, erasure coding support, and integration with Kerberos and LDAP for authentication and authorization. Clients may mount repositories via POSIX-compatible modules or access objects via RESTful APIs used by analysis frameworks such as ROOT and workflow managers employed by collaborations like HTCondor.

Performance and Scalability

EOS targets low-latency metadata operations and high aggregate bandwidth for parallel I/O typical of workflows in High Energy Physics experiments. Benchmarks reported by operations teams compare EOS throughput against systems such as CephFS and GPFS under workloads driven by Monte Carlo production and detector reconstruction. Scalability design leverages sharded namespace managers and a data-plane composed of many commodity servers, enabling deployments across compute clusters managed by orchestration platforms like Kubernetes or site-level schedulers such as Slurm.

Deployment and Use Cases

EOS is widely deployed at CERN as the primary disk storage for LHC runs and is used by experiments ALICE, LHCb, in addition to ATLAS and CMS. It supports user analysis, staged workflows to tape managed by CASTOR-like systems historically, and as a backend for data lakes and cache layers in federations including WLCG and national grid infrastructures such as GridPP. Administrators integrate EOS with identity providers like CERN SSO and monitoring stacks used by Site Reliability Engineering teams; data managers use EOS features for lifecycle policies, replication to remote tiers, and burst-buffering for HPC campaigns hosted at sites such as PRACE centers.

Development History and Versioning

EOS development began within CERN to replace older storage subsystems and to provide a modern, maintainable codebase for long-term experiments. The project evolved through major releases and feature-driven milestones coordinated by infrastructure groups and presented at conferences such as CHEP and Grid2003-era meetings. Versioning follows semantic practices with changelogs maintained in repositories hosted on platforms like GitLab; contributions come from institutional teams across Europe and partner laboratories such as Fermilab and national research computing centers.

Security and Data Integrity

EOS implements access controls integrated with Kerberos and LDAP identity providers and supports TLS for secure data transfers, aligning with practices used by CERN Computer Security Team and federated authentication initiatives like eduGAIN. Data integrity mechanisms include checksums, replication policies, and support for erasure coding to protect against disk and server failures; archival tiers interface with tape systems from vendors like IBM and HPE for long-term preservation. Operational security relies on monitoring, incident response coordination with groups such as CERT teams at participating institutions, and compliance with data stewardship policies adopted by international collaborations.

Category:Distributed file systems