> On May 19, 2015, at 11:40 AM, Schneider, David A. > <[email protected]> wrote: > > When working from hdf5 and mpi, I have seen a number of references about > tuning parameters, I haven't dug into this yet. I first want to make sure > lustre has the high output performance at a basic level. I tried to write a C > program uses simple POSIX calls (open and looping over writes) but I don't > see much increase in performance (I've tried 8 and 19 OST's, 1MB and 4MB > chunks, I write a 6GB file). > > Does anyone know if this should work? What is the simplest C program I could > write to see an increase in output performance after I stripe? Do I need > separate processes/threads with separate file handles?
If you are looking for a simple shared-file test, you could try something like this: 1) Create a file with a stripe size of 1 GB and a stripe count of 6. 2) Write an MPI program where each process writes 1 GB of sequential data. Each process should first seek to (mpi_rank)*(1GB) and then write 1 GB. This will ensure that all processes are writing to non-overlapping parts of the file. 3) Start the program running on 6 nodes (1 process per node). In a scenario like that, you should effectively be getting file-per-process speeds even though you are writing to a shared file because each process is writing to a different OST. -- Rick Mohr Senior HPC System Administrator National Institute for Computational Sciences http://www.nics.tennessee.edu _______________________________________________ lustre-discuss mailing list [email protected] http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org
