Hi Mohamad, Thanks for the reply! 1) I actually don't know, I just turned the flag on 2) I can't change the values on the fly as in the same folder, I have different kind of files (text, binary, HDF5), and the HDF5 file has to be created from scratch. Due to the issues with the Lustre API (license + unstable ABI), I can't integrate it inside the application :/ The current stripe size/count is set for applications that write bigger datasets/files, so I think they are adequately set up by default. Anyway, a raw pwrite performs better, so I can tune this later.
Regards, Matthieu 2014/1/22 Mohamad Chaarawi <[email protected]>: > Hi Matthieu, > > No, nothing different happens internally when handling larger datasets. > > Some questions to understand more what you are doing: > 1) what VFD are you using? I assume it's the MPIO VFD since you said HDF5 > with parallel Processes, but you didn't say that explicitly. > 2) Did you make sure your Lustre stripe settings (stripe count and size) are > appropriate? i.e. the larger amount of data you write, the larger your stripe > settings must be. > > Those are the only 2 things I can think of without looking at your code. > > Thanks, > Mohamad > > -----Original Message----- > From: Hdf-forum [mailto:[email protected]] On Behalf Of > Matthieu Brucher > Sent: Tuesday, January 21, 2014 2:25 PM > To: HDF Users Discussion List > Subject: [Hdf-forum] Performance hit when writing to big datasets > > Hi, > > I noticed today something strange. I've been using HDF5 with parallel > processes, and when I raise the dataset size, the library seems to slow down. > Currently, I have a fixed number of processes writing data from my > simulation. All these processes write 1MB concurrently to contiguous but > exclusive locations in the 1D dataset. When having more than 1 billion > elements (for instance), the library is getting really, really slow (more > than 20 times slower than what a usual pwrite would take), where as nothing > can be noticed when writing say 1 million cell. > Is there something fancy going on? I'm trying to access the simplest part of > the library so that the H5write call can be more or less reduced to a pyrite > call, but something is wrong. Should I set something to tell HF5 than it > shouldn't do anything except than writing data from the calling process to > the filesystem (Lustre in my case, MPI library configured with Lustre > support). > > Regards, > > Matthieu Brucher > -- > Information System Engineer, Ph.D. > Blog: http://matt.eifelle.com > LinkedIn: http://www.linkedin.com/in/matthieubrucher > Music band: http://liliejay.com/ > > _______________________________________________ > Hdf-forum is for HDF software users discussion. > [email protected] > http://mail.lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org > > _______________________________________________ > Hdf-forum is for HDF software users discussion. > [email protected] > http://mail.lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org -- Information System Engineer, Ph.D. Blog: http://matt.eifelle.com LinkedIn: http://www.linkedin.com/in/matthieubrucher Music band: http://liliejay.com/ _______________________________________________ Hdf-forum is for HDF software users discussion. [email protected] http://mail.lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org
