steve traylen particle physics department experiences of dcache at ral uk hep sysman, 11/11/04 steve...
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Steve Traylen
Particle Physics Department
Experiences of DCache at RALUK HEP Sysman, 11/11/04
Steve [email protected]
Steve Traylen
Particle Physics Department, Rutherford Lab
DCache Origins
• Developed and maintained by Fermilab and DESY.
• Used extensively by Zeus/H1 at DESY.
• Designed primarily to sit in front of a tape store.
Steve Traylen
Particle Physics Department, Rutherford Lab
Why DCache
• Gives you a virtual filesystem across many file systems optionally on several nodes.
• Allows replication within filesystem to increase redundancy.
• Allows a tape system to be interfaced at the back to increase redundancy further.
• Data protocols are scalable, one GridFTP interface per server is easy and transparent.
Steve Traylen
Particle Physics Department, Rutherford Lab
DCache Doors
• Doors can be created into the system.– GridFTP– SRM– GSIDCAP
• A POSIX interface is available to this.• All of these are GSI enabled but Kerberos doors
also exist.• Everything remains consistent regardless of the
door that is used. – A big advantage over the edg-se.
Steve Traylen
Particle Physics Department, Rutherford Lab
History of DCache at RAL• Mid 2003
– We deployed a non grid version for CMS. It was never used in production.
• End of 2003/Start of 2004
– RAL offered to package a production quality DCache.
– Stalled due to bugs and went back to developers and LCG developers.
Steve Traylen
Particle Physics Department, Rutherford Lab
DCache today at RAL
• September 2004
– Redeployed DCache into LCG system for CMS and DTeam VOs.
– In production, yet to be proved.
• Deployed within JRA1 testing infrastructure for gLite i/o daemon testing.
Steve Traylen
Particle Physics Department, Rutherford Lab
Current Deployment at RAL
Steve Traylen
Particle Physics Department, Rutherford Lab
Transfer into DCache
Steve Traylen
Particle Physics Department, Rutherford Lab
Transfer into DCache
Steve Traylen
Particle Physics Department, Rutherford Lab
Upcoming Deployments
• Both LHCb and Atlas want a DCache setup.
– This is happening now.
• LHCb also wants the system backed to the ADS.
– At this time this has not been investigated but will be by the tier1 or the storage group.
Steve Traylen
Particle Physics Department, Rutherford Lab
Extreme Deployment.
Steve Traylen
Particle Physics Department, Rutherford Lab
Current Installation Technique
• The tier1 now has its own cookbook to follow but is not generic at this time.
• Prerequisites– VDT for certificate infrastructure.– edg-mkgridmap for grid-mapfile.– J2RE.– Host certificate for all nodes with a GSI
door.
Steve Traylen
Particle Physics Department, Rutherford Lab
RPM Packages
• Head NODE
– d-cache-client, d-cache-lcg, d-cache-core, d-cache-opt and pnfs
• Pool NODE
– d-cache-lcg and d-cache-core.
Steve Traylen
Particle Physics Department, Rutherford Lab
Configuration
• Change a few files and run some scripts with arguments.
• The scripts do a lot so fixing any problems at this stage is difficult and has required expert help.
Steve Traylen
Particle Physics Department, Rutherford Lab
Comments
• Documentation is severely lacking for the operation of DCache.
– E.g There is admin interface accessible via ssh where pools can be marked read only, possibly drained,….
– Trial and error is the standard method.
• With the LCG release a admin guide is promised.
Steve Traylen
Particle Physics Department, Rutherford Lab
Unanswered Questions
• How do we drain a node for maintenance?
– CHEP papers suggest this is possible.
• How do we use one dCache for multiple VOs?
– Is there a concept of defining quotas for groups?
– Can we tie one group to specific nodes.