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xrootd Update

xrootd Update. OSG All Hands Meeting University of Nebraska March 19-23, 2012 Andrew Hanushevsky, SLAC http://xrootd.org. Outline. Additions & Changes (available now in 3.1.1) On the horizon (anticipated for 3.2 release 3Q12) Near future (anticipated for 3.3 release)

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xrootd Update

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  1. xrootd Update OSG All Hands Meeting University of Nebraska March 19-23, 2012 Andrew Hanushevsky, SLAC http://xrootd.org

  2. Outline • Additions & Changes (available now in 3.1.1) • On the horizon (anticipated for 3.2 release 3Q12) • Near future (anticipated for 3.3 release) • The xrootd collaboration • Conclusion • Acknowledgements

  3. Additions & Changes (3.1) • Extended Attribute Framework • Integrated checksums • Shared-Everything File System Support • Static ENOENT redirection • Enhances creation of new topologies • Caching proxy server • Federated site shares • Monitoring Extended • Read-fork-read client

  4. Agnostic Extended Attributes • FS-Independent Extended Attribute Framework • Used to save file-specific information • File system must support extended attributes • Current Attributes • XrdCks.xxxxxx (e.g. md5) checksum • XrdFrm.yyyFile Residency Manager information • Future Attributes • Original file creator • Extended Access Information • Number of parallel readers, % read, access time • Can be used for better migration/purging

  5. Integrated Checksums • Originally, checksums supported via callout • Now, xrootd internally handles checksums • xrootd.chksum [maxnum] {adler32|crc32|md5} • Add new ones via ofs.ckslib directive and plug-in • Checksum saved in extended attributes • Returned on query • Automatically recomputed when file changes • Can be disabled • External program not needed; but still supported

  6. Shared FS Support • The problem dCache GPFS HDFS Lustre etc Data Server Client Redirector Data Server Shared FS Data Server open(x) have(x) stat(x) • The solution • Use cms.dfs directive to eliminate duplicate hits • Many tuning options available • Lookup at redirector, limits, caching, etc • See http://xrootd.org/doc/prod/cms_config.htm

  7. Static ENOENT Redirection ? xyzzy:1234 open(x) Data Server goto xyzzy:1234 if redirector_host xrootd.redirect ? / xyzzy:1234 fi Client Redirector Data Server open(x) Data Server have(x) • What we envisioned. . . • xyzzy is a caching proxy server or proxy cluster • Provides high performance WAN access • Client accesses data via WAN in this case

  8. What Others Envisioned! open(x) Global Redirector Client all.manager meta C all.manager meta global if redirector C xrootd.redirect ? / global:1234 fi goto xyzzy:1234 exclude region A open(x) ? Redirector A Redirector B Redirector C Site 8 Site 7 Site 5 Site 6 Site 4 Site 3 Site 2 Site 1 Region A Region B Region C

  9. Caching Proxy Server • The proxy server plug-in has in-memory cache • Must be enabled via pss.memcache directive • Many tuning options; some of which are . . . • Cache and page size • Read ahead size • Maximum block size to cache • Root file access optimization • See http://xrootd.org/doc/prod/ofs_config.htm

  10. Federated Site Shares • The problem Each site gets an equal number of requests all things being equal Site A Meta Manager Site B Site C Client • What to do if sites do not want to be equal? • Use cms.sched directive to establish site share • Use the gshr and gsdflt options • See http://xrootd.org/doc/prod/cms_config.htm

  11. Monitoring • Readv requests fully monitored • By default, only a readv request summary provided • Can request a full unwind of a readv request • Per client I/O monitoring now flushable • Before, I/O statistics flushed when buffer full • Can specify a flush window • Based on code provided by MatevzTadel, CMS • Authentication can now be fully monitored

  12. Read-Fork-Read Client • The current client allows forking • This allows sharing data between processes • Read conditions data • Fork n times for parallel processing • Read event data using pre-read conditions data • Extensively used by CMS • Substantially reduces memory load • Critical for large multi-core worker nodes

  13. git & cmake & EPEL • Now using git repository for source code • git clone http://xrootd.org//repo/xrootd.git • Standardized on cmake for builds • See README file in the top level source directory • Adhering to EPEL guidelines • All ‘.a’ files are replaced by ‘.so’ files • Caused increase in number of installed .so files • We consolidated libraries; but more than we would like • Unfortunately, changing things afterwards is difficult in EPEL

  14. On the horizon (3.2) • New fully asynchronous client • Guards against low performing servers • To be added in subsequent release • Extended monitoring • Redirect information • Authentication summary information • Integrated 3rd party copy • Allows client directed server-to-server copies • Dropping RH4 support

  15. Things Within A Year (3.3+) • Disk Caching Proxy Server • Extension of memory caching (UCSD effort) • Automatic checksum validation • Integrated alerts • New more effective async I/O model • IPV6

  16. Xrootd Collaboration • Mutually interested institutions contributing effort for development and maintenance • SLAC (founder) • CERN (2010) • Duke (spring 2011) • JINR (fall 2011) • UCSD (winter 2011) • Newest member!

  17. Conclusion • xrootdis under active development • Always looking for new ideas • Feel free to suggest them • Be a contributor • You too can contribute to the code base • Consider joining the xrootdcollaboration • It costs no money to join • See more at http://xrootd.org/

  18. Acknowledgements • Current Software Contributors • ATLAS: Doug Benjamin, Patrick McGuigan, DanilaOleynik, ArtemPetrosyan • CERN: FabrizioFurano, Lukasz Janyst, Andreas Peters,David Smith • CMS: Brian Bockelman (unl), MatevzTadel (ucsd) • Duke: Douglas Benjamin • Fermi/GLAST: Tony Johnson • LBNL: Alex Sim, JunminGu, VijayaNatarajan(BeStMan team) • Root: Gerri Ganis, BeterandBellenet, FonsRademakers • OSG: Tim Cartwright, Tanya Levshina • SLAC: Andrew Hanushevsky,WilkoKroeger, Daniel Wang, Wei Yang • Operational Collaborators • ANL, BNL, CERN, FZK, IN2P3, SLAC, UCSD, UTA, UoC, UNL, UVIC, UWisc • US Department of Energy • Contract DE-AC02-76SF00515with Stanford University

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