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color=#0000ff size=2>Which file system you use matters because different file
systems have different consistency semantics, and we accordingly have to
compensate for it in order to provide complete MPI-IO functionality. If you
are using NFS, you pretty much need locks to work unless you are only doing
reads from the file. On a true POSIX file system, you need locks to implement
shared file pointer, the atomic mode, and the data sieving optimization for
noncontiguous writes (which can be disabled with an info hint). We have come up
with a way to avoid locks on a POSIX file system by implementing the
equivalent of locks with MPI one-sided communication, and have 3 papers on
it, but it is not in the ROMIO release yet. (Locks will still be needed on NFS
to disable client-side caching.)</FONT></SPAN></DIV>
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<DIV dir=ltr align=left><SPAN class=370464521-21062005><FONT face=Arial
color=#0000ff size=2>Rajeev</FONT></SPAN></DIV>
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<FONT face=Tahoma size=2><B>From:</B> owner-mpich-discuss@mcs.anl.gov
[mailto:owner-mpich-discuss@mcs.anl.gov] <B>On Behalf Of </B>Foucar, James
G<BR><B>Sent:</B> Tuesday, June 21, 2005 4:34 PM<BR><B>To:</B> Rajeev Thakur;
mpich-discuss@mcs.anl.gov<BR><B>Subject:</B> RE: [MPICH] tricks for avioding
locking problems<BR></FONT><BR></DIV>
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<P><FONT size=2>Let's not focus on NFS at the moment. What I really need is a
way, trick, or hack that allows me to circumvent or disable file locking in
general. Does such a thing
exist?<BR><BR>Thanks,<BR>Jim<BR><BR><BR>-----Original Message-----<BR>From:
Rajeev Thakur [<A
href="mailto:thakur@mcs.anl.gov">mailto:thakur@mcs.anl.gov</A>]<BR>Sent: Tue
6/21/2005 3:25 PM<BR>To: Foucar, James G;
mpich-discuss@mcs.anl.gov<BR>Subject: RE: [MPICH] tricks for avioding locking
problems<BR><BR>One way to avoid this problem is to not use NFS :-).<BR><BR>Do
you have the lockd daemon running on all
nodes?<BR><BR>Rajeev<BR><BR><BR> _____ <BR><BR>From:
owner-mpich-discuss@mcs.anl.gov<BR>[<A
href="mailto:owner-mpich-discuss@mcs.anl.gov">mailto:owner-mpich-discuss@mcs.anl.gov</A>]
On Behalf Of Foucar, James G<BR>Sent: Tuesday, June 21, 2005 4:12 PM<BR>To:
mpich-discuss@mcs.anl.gov<BR>Subject: [MPICH] tricks for avioding locking
problems<BR><BR><BR><BR>Hello,<BR><BR>I was wondering if any of you know of
ways to avoid the following error:<BR><BR>> File locking failed in
ADIOI_Set_lock. If the file system is NFS, you<BR>> need to use NFS version
3 and mount the directory with the 'noac' option<BR>> (no attribute
caching).<BR>> [0] MPI Abort by user Aborting program !<BR>> [0]
Aborting program!<BR>> p0_928: p4_error: : 1<BR>> exit
1<BR><BR>This error, and similar errors, have popped up randomly on all many
file<BR>systems, regardless of whether they were mounted with attribute
caching.<BR><BR>I have tried using the MPI_MODE_UNIQUE_OPEN flag when opening
files and some<BR>other tricks, but nothing seems to get rid of this problem
permanently on<BR>all the various platforms that I need to
support.<BR><BR>What I really need is a general way to tell MPICH not to use
any file<BR>locking or at least some way to avoid this
error.<BR><BR>Thanks!<BR>-Jim<BR><BR><BR></FONT></P></BLOCKQUOTE></BODY></HTML>