Some comments after the talk of Graeme at GDB of 11 Feb 2009

Short chat with Graeme after the GDB: in general (except 2 sites which have major problems...) the overall performance of SRM was quiet good. Of course one has to remember that there was no other activity, of other VOs, going on at the same time (which is not realistic...). An extremely interesting test would be to run simultaneously a similar test for CMS and ATLAS.

The fact of using srmLs instead the statusOfxxx is not really an issue for them. They have not observed the problem mentioned by Flavia about the fact that srmLs was returning the status of another copy of the file, staged in a previous operation. Flavia had observed this problem several times at SARA. The origin of the problem was that the request was sitting in the queue for a very long time before being processed. So the overall time to fulfill a request to stage a file which had already a copy on disk (which, in principle, should take fractions of a second!) was taking very long time. Question: could it be that this problem was very much dependent on the particular configuration of dCache at SARA? The fact that a request sits in the queue for a time much longer than the time needed to fulfill the request itself looks like a serious inefficiency. Maybe the server was configured in a very inefficient way...

The most annoying thing is that they lost some files. Even if they are very few files, it is very inefficient to recover them by hand afterward. See also here for the follow up of this problem.

An observation: in general it was more problematic to have their tests working fine at dCache sites than at CASTOR sites, because of the extreme variety of configurations of dCache: basically in every site it works in a different way and present different issues.

About the life time of the request: Graeme would be very much interested in using this time as a timeout for the polling mechanism, in order not to overload the server. See also here for the follow up of this problem.

-- ElisaLanciotti - 13 Feb 2009

Edit | Attach | Watch | Print version | History: r1 | Backlinks | Raw View | WYSIWYG | More topic actions
Topic revision: r1 - 2009-06-05 - AndreaSciaba
 
    • Cern Search Icon Cern Search
    • TWiki Search Icon TWiki Search
    • Google Search Icon Google Search

    LCG All webs login

This site is powered by the TWiki collaboration platform Powered by PerlCopyright & 2008-2019 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback