19 September 2018

When did we switch storage systems.... I'm not sure I can tell.....

So as part of the Storage evolution within the UK, the Birmingham site is switching SEs from DPM to EOS for the ATLAS experiment. However this blog isn't about that, this blog is about what is happening in the meantime... Similar to the way in which we pointed UCL WNs to use QMUL storage in London, ATLAS have switched the 'Brum' WNs to use storage at Manchester. This "greatly" increases the rtt between WN and SE from ~0.1ms to ~4ms. So I got to wandering, is this increase in latency noticeable in Job efficiency for the VOs. Here are the graphs from the VO for Birmingham and Manchester for the last month..
For Manchester a a control set for SE performance we have:

And for Birmingham we have:

I leave it to the reader to come to conclusions about wether Birmingham efficiencies have dropped since changing SEs. (Even if that conclusion is "you need more data to make a proper comparison",) but at least its something to get things going...

11 September 2018

40/100G networks are here! (but also have been for a while...)

So hearing that RAL now has a 100G link into JANET started me thinking again about what kind of network tuning might be needed.. A quick bit of using a popular search engine (and knowledge that their are certain individuals I have found that can provide useful info on this area, I found:



What surprised me (and shouldn't have) was how old these posts were! Of particular interest has been that there really is a benefit to get diskservers upgraded to SL/CENTOS 7 rather than 6. I also did not know there was a 2G limit for TCP window size.

Successful DPM/DOME BOF/Hackathon

As part  of a side meeting to the GRIDPP41 meeting held in Ambleside this year, we also had a successful BOF/Hackathon meeting. Now I probably should care more about the WN configuration/security hack session, but that really is SEP to me. However the discussion we had regarding Lancaster's DOME deployment  and DPM legacy mode in general was useful to understand the DPM roadmap and how we are going to roll out SRM less service at  tier 2 sites. This is germane at the moment as some of the features such as 3rd party copy (or TPC as it shall now be known as...) are needed for supporting data activities not just for the WLCG VOs but also some of our smaller communities. (DUNE is an example.)