[Beowulf] Can one Infiniband net support MPI and a parallel file system?

Robert Latham robl at mcs.anl.gov
Wed Aug 13 14:38:53 EDT 2008

On Wed, Aug 06, 2008 at 01:31:09PM -0500, Jason Clinton wrote:
> Generally speaking, MPI programs will not be fetching/writing data
> from/to storage at the same time they are doing MPI calls so there
> tends to not be very much contention to worry about at the node level.

Well... if the MPI program uses collective I/O (maybe they use
MPI_File_write_all directly, or they are using collective
parallel-NetCDF or parallel-HDF5 calls),  it is likely the MPI-IO
implementation will optimize that access with "two-pase" buffering.

I would like to think this situation is common in high performance
I/O, especially when accessing a parallel file system.  Some
tremendous performance gains can be had with collective I/O.


Rob Latham
Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
Argonne National Lab, IL USA                 B29D F333 664A 4280 315B
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