Most users do not need to worry about file systems. However, there are two issues: using NFS (the Network File System) with MPI-IO and using NFS with some automounters. These issues are covered in the next two sections.
To use MPI-IO multihost on NFS file systems, NFS should be version 3, and the
shared NFS directory must be mounted with the ``no attribute caching'' (noac)
option set (the directory cannot be automounted). If NFS is not mounted
in this manner, the following error could occur:
MPI_Barrier: Internal MPI error: No such file or directory
File locking messages
In order to reconfigure NFS to handle MPI-IO properly, the following sequence
of steps are needed (root permission required):
rpcinfo -p `hostname` | grep nfs
for example, there should be a '3' in the second column
fire >rpcinfo -p fire | grep nfs
100003 3 udp 2049 nfs
root >grep epm1 /etc/fstab
gershwin:/epm1 /rmt/gershwin/epm1 nfs bg,intr,noac 0 0
If the ``noac'' option is not present, add it and then remount this
directory on each of the machines that will be used to share MPI-IO files.
root >umount /rmt/gershwin/epm1
root >mount /rmt/gershwin/epm1
root >grep gershwin /etc/mnttab
gershwin:/epm1 /rmt/gershwin/epm1 nfs
noac,acregmin=0,acregmax=0,acdirmin=0,acdirmax=0 0 0 899911504