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Xrootd Topology

Xrootd Topology. FAX Meeting September 11, 2012 Andrew Hanushevsky, SLAC http://xrootd.org. Goals. Describe basic xrootd clustering The basic topology Describe extended xrootd clustering The stacked (two level) topology Describe upstream redirection Why it’s essential to locality

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Xrootd Topology

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  1. Xrootd Topology FAX Meeting September 11, 2012 Andrew Hanushevsky, SLAC http://xrootd.org

  2. Goals • Describe basic xrootdclustering • The basic topology • Describe extended xrootd clustering • The stacked (two level) topology • Describe upstream redirection • Why it’s essential to locality • Describe A Typical Federated Topology • The multi-level forest topology

  3. xrootdStorage Clustering • An xrootdserver “always”s runs a process pair • Symmetric cookie-cutter arrangement • The xrootd process provides data access • Plus authentication and access control • The cmsdprocess clusters xrootdservers • Monitors xrootdhealth • Reports load and space usage • Checks for file existence upon request • From another cmsd xrootd cmsd

  4. Basic Topology • Basically, an xrootdcluster is a tree • The root is a redirector that chooses a leaf • The leaves are data providers • But this is all relative, as we shall see later Redirector xrootd cmsd Data Providers

  5. A Simple xrootd Cluster Manager (a.k.a. Redirector) 1: open(“/my/file”) Client 4: Try open() at A xrootd xrootd xrootd xrootd cmsd cmsd cmsd cmsd 5: open(“/my/file”) 3: I DO! 3: I DO! 2: Who has “/my/file”? Data Servers xrootd A /my/file B C /my/file cmsd

  6. Extending The Topology • Building blocks are stackable & replicable • Can create a wide variety of configurations • Much like you would do with LEGOÒ blocks • We use the capability to federate clusters • Essentially creating clusters of clusters • While topologically simple • It can look more complicated than it really is xrootd cmsd

  7. Two Level Topology • A federated xrootdcluster is a tree of trees • Essentially a forest • The root redirector chooses a sub-tree • The sub-tree root is a redirector that chooses a leaf • The end-point leaves are data providers Redirector (aka meta-manager) Redirector (aka manager) xrootd cmsd Data Providers

  8. Federation In Xrootd Client Meta-Manager (a.k.a. Global Redirector) S e r v e r s S e r v e r s S e r v e r s Data is uniformly available By federating three distinct sites 1: open(“/my/file”) 2: Who has “/my/file”? 5: Try open() at ANL 7: Try open() at A 6: open(“/my/file”) 4: I DO! 4: I DO! Manager (a.k.a. Local Redirector) Manager (a.k.a. Local Redirector) Manager (a.k.a. Local Redirector) xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd xrootd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd cmsd 8: open(“/my/file”) B xrootd A C /my/file ANL SLAC UTA C C C /my/file /my/file /my/file cmsd An exponentially parallel search! (i.e. O(2n)) A A A /my/file /my/file B B B Federated Distributed Clusters Distributed Clusters 3: Who has “/my/file”? 3: Who has “/my/file”? 3: Who has “/my/file”?

  9. Top Down vs Bottom Up • You might think access is always top down • So that you get to see all of the available data • But that would make locality impossible • So, we use upstream redirection when needed Redirector (aka meta-manager) If File Not Found Get file From root But avoid A A + B + C Redirector (aka manager) Get file From A xrootd A B C cmsd Data Providers

  10. A More Typical Topology What Is The Data Leaf Search Order? If File Not Found Get file From EU But avoid US If File Not Found Get file From US But avoid B US EU 3 3 4 A B C X W+V Y+Z 2 4 1 4 4 4 xrootd If File Not Found Get file From B But avoid D Get file From D D E Y Z W V cmsd

  11. Acknowledgements • Current Software Contributors • CERN: FabrizioFurano, Lukasz Janyst, Andreas Peters,David Smith • Duke: Doug Benjamin • EPEL: MattiasEllert, Ricardo Rocha • Fermi/GLAST: Tony Johnson • LBNL: Alex Sim, JunminGu, VijayaNatarajan(BeStMan team) • OSG: Tim Cartwright, Tanya Levshina • Root: Gerri Ganis, BeterandBellenet, FonsRademakers • SLAC: Andrew Hanushevsky,WilkoKroeger, Daniel Wang, Wei Yang • UCSD: MatevzTadel • UNL: Brian Bockelman • The xrootdCollaboration • CERN, Duke, JINR, SLAC, UCSD • US Department of Energy • Contract DE-AC02-76SF00515with Stanford University

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