22 May 2012

CHEP Day 1 - some notes

So, Wahid and I are amongst the many people at CHEP in New York this week, so it behooves us to give some updates on what's going on. The conference proper started with a long series of plenary talks; the usual Welcome speech, the traditional Keynote on HEP and update on the LHC experience (basically: we're still hopeful we'll get enough data for an independent Higgs discovery from ATLAS and CMS; but there's a lot more interesting stuff that's going on that's not Higgs related - more constraints on the various free constants in the Standard Model, some additional particle discoveries).

 The first "CHEP" talk in the plenary session was given by Rene Brun, who used his privilege of being the guy up for retirement to control the podium for twice his allocated time; luckily, he used the time to give an insightful discussion of the historical changes that have occurred in the HEP computing models over the past decades (driven by increased data, the shifting of computational power, and the switch from Fortran (etc) to C++), and some thoughts on what would need to form the basis of the future computing models. Rene seemed keen on a pull model for data, with distributed parallelism (probably not at the event level) - this seems to be much more friendly to a MapReduce style implementation than the current methods floating around.
 There was also a talk by the Dell rep, Forrest Norrod, on the technology situation. There was little here that would surprise anyone; CPU manufacturers are finding that even more cores doesn't work because of memory bandwidth and chip real-estate issues, so expect more on-die specialised cores (GPUs etc) or even FPGAs. The most interesting bit was the assertion that Dell (like HP before them) are looking at providing an ARM based compute node for data centres. After a lunch that we had to buy ourselves, the parallel sessions started.

The Distributed Processing track began with the usual traditional talks - Pablo Saiz gave an overview of AliEn for ALICE, they're still heavily based on xrootd and bittorrent for data movement, which sets them apart from the other experiments (although, of course, in the US, xrootd is closer to being standard); Vincent Garonne gave an update on ATLAS data management, including an exciting look at Rucio, the next-gen DQ2 implementation; the UK's own Stuart Wakefield gave the CMS Workload Management talk, of which the most relevant data management implication was that CMS are moving from direct streaming of job output to a remote SE (which is horribly inefficient, potentially, as there's no restriction on the destination SE's distance from the site where the job runs!) to an ATLAS-style (although Stuart didn't use that description ;) ) managed data staging process where the job output is cached on the local SE then transferred to its final destination out-of-band by FTS.
Philippe Charpentier's LHCb data talk was interesting primarily because of the discussion on "common standards" that it provoked in the questions - LHCb are considering popularity-based replica management, but they currently use their own statistics, rather than the CERN Experiment Support group's popularity service.
Speaking of Experiment Support, the final talk before coffee saw Maria Girone give the talk on the aforementioned Common Solutions strategy, which includes HammerCloud and the Experiment Dashboards as well as the Popularity Service - the most comment came from the final slides, however, where Maria discussed the potential for a Common Analysis Service framework (wrapping, say, a PanDA server so that the generic interfaces allow CMS or ATLAS to use it). There was some slightly pointed comment from LHCb that this was lovely, but they reminded people of the original "shared infrastructure" that LHCb/ATLAS used, until it just became LHCb's...

 After that: coffee, where Rob Fay and I were pounced on by a rep from NexSan, who still have the most terrifyingly dense storage I've seen (60 drives per 4U, in slide-out drive "drawers"), and were keen to emphasise their green credentials. As always, of course, it's the cost and the vendor-awareness issues that stop us from practically buying this kind of kit, but it's always nice to see it around.

 The second and final parallel session of the day saw talks by the UK's own Andy Washbrook and our own Wahid Bhimji, but I didn't make those, as I went to the session ended by Yves Kemp (as Patrick Fuhrmann's proxy) giving the results of DESY's testing of NFS4.1 (and pNFS) as a mountable filesystem for dCache. Generally, the results look good - it will be interesting to see how DPM's implementation compares when it is stable - and Yves and I discussed the implications (we hope that) this might have on protocol use by experiments. (We're both in favour of people using sensible non-proprietary protocols, like NFS and HTTP, rather than weird protocols that no-one else has heard of; and the benefits of kernel-level support for NFS4.1 as a POSIX fs are seen in the better caching performance for users, for example).

 Today will see, amongst other things, the first poster session - with 1 hour allocated to see the posters, and several hundred posters all up, we'll have just 15 seconds to appreciate each one; I'll see what the blurry mass resolve to when I do my second CHEP update tomorrow!

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