We had a user run into a situation with ROMIO that caused a bunch of head-scratching before we figured it out. The user was running a trivial C MPI program that failed with a truncation error in MPI_Bcast. After much poking around, we finally figured out that it was actually failing deep within MPI_File_open. The reason it was getting a truncation error is because of the user's setup: - the cluster head node is *also* a compute node - the cluster head node is the NFS server - in MPI_COMM_WORLD rank 0 (on the head node), ROMIO saw a UFS filesystem - all other MCW process ranks saw an NFS filesystem - hence, during ROMIO's MPI_File_open, MCW rank 0 chose to do a UFS file open and everyone else chose to do an NFS file open Things go downhill from there, eventually resulting in a MPI_Bcast mismatch. Is there any thought to supporting this kind of scenario? All MPI processes are accessing the same filesystem; it's just that some of the MPI processes happen to see that filesystem as local, and some see it as NFS. Regardless, if this can't/won't be supported, can there be some kind of Allreduce before calling ADIOI_Open that determines, "Hey, we're not viewing this as the same filesystem -- we should throw an error (and possibly print a helpful error message)." Such cluster configurations are not entirely uncommon; being able to error out with a user-helpful reason would be most helpful. -- Jeff Squyres [email protected] For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/