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XRootD

XRootD. LSST Data Management Database Architecture Review SLAC National Accelerator Laboratory August 6-7, 2013 Andrew Hanushevsky, SLAC http://xrootd.org. A Bit Of XRootD History. 1997 – Objectivity, Inc. collaboration Design & Development to scale Objectivity/DB

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XRootD

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  1. XRootD LSST Data Management Database Architecture Review SLAC National Accelerator Laboratory August 6-7, 2013 Andrew Hanushevsky, SLAC http://xrootd.org

  2. A Bit Of XRootDHistory • 1997 – Objectivity, Inc. collaboration • Design & Development to scale Objectivity/DB • First attempt to use commercial DB for Physics data • Successful but problematical • 2001 – BaBar decides to use root framework vs Objectivity • Collaboration with INFN, Padova & SLAC created • Design & develop high performance data access system • Work based on what we learned with Objectivity • 2003 – First deployment of XRootDsystem at SLAC • 2013 – Wide deployment in LHC & Astrophysics • ALICE, ATLAS, CMS, EXO, Fermi/GLAST, LSST; among others • Protocol also available in dCache, DPM, and EOS

  3. What IsXRootD? • A system for scalable cluster data access • Not a file system & not just for file systems • If you can write a plug-in you can cluster it • The essential key for Qserv cmsd Data Access Data Clustering xrootd

  4. Authentication krb5 sss x.509 … Protocol cms http xroot … Authorization Entity Names Logical File System (OFS Plugin) Scalable Service Interface Qserv Plus mySQL Storage System HDFS gpfsLustre UFS, … Logical File System dpmsfssql … Clustering (cmsd) Clustering (cmsd) XRootDPlug-In Architecture Protocol Driver Any n protocols 4

  5. The Original Challenge • The physics analysis regime “problem” • Write once read many times access mode • Small block sparse random I/O • Hundreds of servers of uneven reliability • Thousands parallel batch jobs • 100’s of thousands file sessions The LSST Challenge

  6. XRootDSynergistic Solution Minimizelatency Parallelizable protocol, file sessions, lockless I/O, sticky threads Minimize hardware requirements Short code paths, compact objects Cache aware members Minimal data movement No cross-thread data sharing Minimize human cost Single configuration file Cookie cutter installation No database needed Real time node change, Native FS admin tools Maximize scaling Result <7 us overhead & <100 MB footprint & unlimited servers 6

  7. XRootD B64 Scaling xrootd cmsd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd Replicated & Load Balanced cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd Manager (Root Node) 641 = 64 642 = 4096 Supervisors (Interior Nodes) 643 = 262144 644 = 16777216 Data Servers (Leaf Nodes) Qserv worker nodes reside only at the leaves Each identified by a dynamic set of arbitrary names

  8. WYSIWYG Scalable Access xrootd cmsd open() redirect Client open() redirect open() xrootd xrootd xrootd xrootd xrootd xrootd xrootd cmsd cmsd cmsd cmsd cmsd cmsd cmsd Request routed to an alternate node exporting same logical name open() Exponentially Parallel Query For Logical Endpoint Name Routing Paths Cached At Each Router Node 641 = 64 642 = 4096 Request routing is very different from traditional data management models This implements a structured network of request routers Capable of automatically recovering from adverse conditions Much like internet routing

  9. Conclusion • A facile, flexible, and sound system • Applicable to a wide variety of problems • LGPL open-source • Managed by the XRootDcollaboration • SLAC, CERN, Duke, JINR, UCSD, & UNL (fall) • More at http://xrootd.org/

  10. Acknowledgements • Current Contributors • ATLAS: Doug Benjamin, Patrick McGuigan, IlijaVukotic • CERN: Lukasz Janyst, Andreas Peters, Justin Salmon • Fermi: Tony Johnson • JINR: DanilaOleynik, ArtemPetrosyan • Root: Gerri Ganis, Bertrand Bellenet, FonsRademakers • SLAC: Andrew Hanushevsky,WilkoKroeger, Daniel Wang, Wei Yang • UCSD: MatevzTadel, AljaMrak-Tadel • UNL: Brian Bockelman • WLCG: FabrizioFurano, David Smith • US Department of Energy • Contract DE-AC02-76SF00515with Stanford University

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