[mpich-discuss] PVFS2/OrangFS with ROMIO ( perf.c )

[Ammar Ahmad Awan]

Dear All,

I am very new to parallel file systems. I am trying to learn how to
use PVFS using ROMIO. The romio source has a test directory which
contains perf.c file.

I am compiling perf.c as follows

mpicc perf.c -o perf.o

I run it like

mpirun -np 2 ./perf.o -fname tesfile

This works fine and gives me the results as

Access size per process = 4194304 bytes, ntimes = 5
Write bandwidth without file sync = 2751.942262 Mbytes/sec
Read bandwidth without prior file sync = 5796.239765 Mbytes/sec
Write bandwidth including file sync = 198.921236 Mbytes/sec
Read bandwidth after file sync = 5482.750327 Mbytes/sec

I want to run it so I can test the performance of my PVFS2
installation. PVFS2 is mounted in /mnt/pvfs2 as per the quick start
guide along with a loaded  kernel module.

My question is when I execute the same perf.c with "pvfs2:" before the
filename like

mpirun -np 2 ./perf.o -fname pvfs2:tesfile

The results that I get are strange. Very high bandwidth but the file
is not created on /mnt/pvfs2. What is the reason that the test
executes but gives the PVFS_util_resolve error and also I cannot see
any file being created on /mnt/pvfs2?

Access size per process = 4194304 bytes, ntimes = 5
PVFS_util_resolve: No such file or directory (error class: 0)
Write bandwidth without file sync = 657930.039216 Mbytes/sec
Read bandwidth without prior file sync = 657930.039216 Mbytes/sec
PVFS_util_resolve: No such file or directory (error class: 0)

Write bandwidth including file sync = 532610.031746 Mbytes/sec
Read bandwidth after file sync = 729444.173913 Mbytes/sec

If I give the full path to the file in the same test like this

mpirun -np 2 ./perf.o -fname /mnt/pvfs2/testfile

The performance reduces and results are :

Access size per process = 4194304 bytes, ntimes = 5
Write bandwidth without file sync = 974.060381 Mbytes/sec
Read bandwidth without prior file sync = 1306.128143 Mbytes/sec
Write bandwidth including file sync = 103.729221 Mbytes/sec
Read bandwidth after file sync = 1261.634532 Mbytes/sec

Can anyone tell me what is the difference between these two methods of
executing ROMIO programs.

1. using the pvfs2: prefix before the filename
2. using the full path to specify the filename without pvfs2: prefix

Which is correct? Both are same?

Kind Regards
-- Ammar
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Masters Student
Dept. Of Computer Engineering,
Kyung Hee University, South Korea
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