DCache Basics Alessandro Usai, Sergio Maffioletti Grid Group CSCS.
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Transcript of DCache Basics Alessandro Usai, Sergio Maffioletti Grid Group CSCS.
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DCache BasicsDCache Basics
Alessandro Usai, Sergio MaffiolettiAlessandro Usai, Sergio Maffioletti
Grid Group CSCSGrid Group CSCS
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
DCache General ArchitectureDCache General Architecture
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
At the core of DCache are subservices (cells) and domains (JVM)
sub-services can run in different locations
DCache is flexibleDCache is flexible
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
General commentsGeneral comments
• It is all Java based i.e. platform independent (in principle)
• It is highly configurable (good) but complex (bad)…the documentation could (needs to) be improved, the logs are obscure (if not absent, unless you explicitly increase the debug level)
• Not easy to maintain upgrades
• Yaim component not powerful enough (i.e. you do it by hand)
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
DCache@CSCSDCache@CSCS
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
In a nutshellIn a nutshell
• Pnfs needs to be mounted by the pool and admin nodes (they need to be authorized)
• Postgres configured to grant the admin node
• Thumpers installed by coping /opt/d-cache from the admin node and changing the configuration where required. Data and Control dirs are placed under /data1 and pointed to via sym links
• CAs and grid-mapfile regular update from CE (via cronjob)
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
Our Pools ConfigurationOur Pools Configuration
• Read only and write only pools (to balance the load)
• p2p enabled (files are replicated for load reasons, only cache copies which get deleted if needed)
• Two movers queues: wan (gridftp) and default (dcap)
• 10 concurrent transfers at a time
• se02-lcg with dteam+ops,cms,atlas and se03-lcg with dteam+ops,cms,atlas,lhcb,hone,dech
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
Some problems we sawSome problems we saw
• Logging obscure (difficult to troubleshoot)
• Domains duplication (as a result we got on board default configuration and a performance hit)
• Timeouts (a known problem still under investigation within the community)
• Various authentication problems due to misconfigurations (e.g. wrong VO tags)
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
How are we doing just now?How are we doing just now?
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
Tips and AdvicesTips and Advices
• Recommended: increase the logging level
• Install srmwatch (beware of the security holes though)
• Get acquainted with the ssh interactive shell on the admin node (ssh -l admin -c blowfish -p 22223 localhost)
• The dcache admin web page is very useful (http://storage01-lcg.projects.cscs.ch:2288/)
• In case off problems [email protected]
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www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS
ReferencesReferences
http://twiki.cscs.ch/twiki/bin/view/LCGTier2/CSCSDCACHE_ausai
http://www.dcache.org/
http://www.dcache.org/manuals/workshop2007/ndgf.shtml