11 December 2012

2nd DPM Community Workshop

The DPM workshop (http://indico.cern.ch/conferenceTimeTable.py?confId=214478#20121203.detailed)
was a very worthwhile meeting and quite well intended in person. It could have done with more people there from the UK - but there were several UK contributions via Vidyo.
On the morning of the first day, Ricardo and Oliver laid out the work so far and roadmap. It was impressive to see that DMLite has becoming a reality with a number of plugins since the last workshop. (And most of this workshop was indeed devoted to DMLite). It was also good to see things like the overloading of disk servers being addressed in the roadmap. We then saw the priorities from other big users, of which it was interesting to see ASGC keen on NFS v4 (which I am not sure we need with xrootd and http) - also they are hosting the next DPM workshop in March collocated with ISGC.

Sam in the Admin Toolkit talk, described plans for rebalancing tool which should probably use DMLite and liase with Ricardo's plans in this area.
The globes online talk did bring up interesting questions of gridftp only transfers as did the ATLAS presentation which talked more explicitly about "ATLAS plans to migrate to a world without srm" then I have heard before, and asked for both performant gridftp transfers and a du solution for directories. The first is being worked on by the DPM team, the last just needs a decision, and ideally a common solution across storage types. CMS seemed happier with DPM in their presentation than they do in normal operations and ALICE seemed happier too now that xrootd is performing well on DPM.

The afternoon was devoted to DMLite and its many interfaces - e.g. S3 and HDFS. Can't wait to play with those in the new year…. Martin presented some interesting things on remote IO performance - certainly xrootd and http offer a much more pleasant direct access experience than rfio (but only with TTreeCache on - which is not guarantied for ATLAS users so we may still be copying to scratch until we can get that switched on by default). We also saw that the WebDav and xrootd implementations are in good shape (and starting to be used - see for example my FAX (ATLAS xrootd) talk - but I think still they need to be tested more widely in production before we know all the bugs). Oliver presented that DPM too was looking to a possible post-SRM landscape and ensuring that their protocols were able to work performantly without it.

Tuesday consisted of a lot of demos showing that DMLite was easy to setup, configure and even develop for (if you missed this then some of the same material was covered in the "Webinar" that should be available to view on the DPM webpages). In addition Ricardo showed how them configure nodes with Puppet and there was a discussion around using that instead of yaim. In the end we decided for "Option 3" - that yaim would be used to generate a puppet manifest that would be run with a local version of puppet on the node so that admins could carry on with yaim for the time being (but it would allow a transition in the future).

The "Collaboration Discussion" that followed was the first meeting of those partners that have offered to help carry DPM forward post-EMI. It was extremely positive in that there seems enough manpower - with core effort at CERN and strong support from ASGC. It seemed like something workable could be formed with tasks divided effectively so there is no need for anyone to fear anymore.

This will be my last blog of the year (possible forever as I dislike blogging) so Happy Holidays Storage Fans!

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