[Pvfs2-users] I/O error

[Michael Kuhn]

Hi,

while doing some I/O visualization we noticed that the attached program
(MPI-IO.c) produces an I/O error under certain circumstances. The error
messages printed by the program (MPI-IO.out) and pvfs2-server
(pvfs2-server.out) are also attached.

The program basically writes and reads data using combinations of
(non-)collective and (non-)contiguous I/O. It seems this error only
occurs if we do non-collective, contiguous I/O (level 0) with multiple
processes. Less processes and other levels work just fine. (The number
of iterations our program does also seems to play a role; 2 iterations
work, 3 produce the error.)

To reproduce, create a default configuration for PVFS2 (data and
metadata on localhost), start pvfs2-server and run the following:

$ mpiexec -np 4 ./MPI-IO -i 10 -f pvfs2:///path/to/pvfs2 level0
# -i controls the number of iterations, -f the file that is written/read

The error occured with PVFS 2.6.2, MPICH2 1.0.5p3 and on several
different machines.

We also noticed that a similar Flow error occurs if the server is low on
free memory. Maybe in this case the error message should be modified to
indicate the lack of memory?


Regards, Michael
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