Good to know. Is it easy to get error detection during MPI_File_open to know that there is a mismatch? On Mar 13, 2014, at 5:33 PM, Rajeev Thakur <[email protected]> wrote:

In such cases, if the user prepends the file name with "nfs:" it should work.

Rajeev

On Mar 13, 2014, at 4:28 PM, Jeff Squyres (jsquyres) <[email protected]> wrote:

...

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/

_______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss

_______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss

-- Jeff Squyres [email protected] For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/