CHEP 2023:
XRD-51 - Getting issue details... STATUS
DRAFT!
The UK Tier-1 facility at RAL provides data access to the LHC and HEP communities via its ECHO storage.
The storage - currently in excess of 40PB of usable space - is deployed as a Ceph-backed erasure-coded object store, with frontend access to data is provided via XRootD - using the XrdCeph plugin - or gridFTP via the libradosstriper library within Ceph.
The storage must service the needs of: high-throughput compute, with staged and direct file access; data access to compute running at storageless sites, increasing utilising XCaches; and, managed inter-site data transfers using the recently adopted HTTP protocol (using WebDav), including multihop data transfers from RAL’s recently commissioned CTA tape endpoint to external sites.
A review of the experiences of running an Object Store within these HEP data workflows, is presented, including the details of the necessary improvements for the transition to WebDav from GridFTP for most inter-site data movements, and enhancements for direct-IO access.
For ROOT-based data formats, the evolution from a TTree to RNTuple data structure provides opportunities for storage providers to optimise against this new format. A comparison of the current performance between data formats within ECHO is made and the details of potential improvements explored .
CHEP 2019:
XRootD and Object Store: A new paradigm
https://doi.org/10.1051/epjconf/202024504006
Abstract
The XRootD software framework is essential for data access at WLCG sites. The WLCG community is exploring and expanding XRootD functionality. This presents a particular challenge at the RAL Tier-1 as the Echo storage service is a Ceph based Erasure Coded object store. External access to Echo uses gateway machines which run GridFTP and caching servers. Local jobs access Echo via caches on every worker node, but it is clear there are inefficiencies in the system. Remote jobs also access data via XRootD on Echo. For CMS jobs this is via the AAA service. ATLAS, who are consolidating their storage at fewer sites, are increasingly accessing job input data remotely. This paper describes the continuing work to optimise both local and remote data access by testing different caching methods.