DCache BasicsDCache Basics

Alessandro Usai, Sergio MaffiolettiAlessandro Usai, Sergio Maffioletti

Grid Group CSCSGrid Group CSCS

www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS

DCache General ArchitectureDCache General Architecture

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

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)

www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS

DCache@CSCSDCache@CSCS

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)

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

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)

www.cscs.chSwiss WLCG Experts Workshop – 11/06/2007 @ CSCS

How are we doing just now?How are we doing just now?

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 user-forum@dCache.ORG

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