[mpich-discuss] ROMIO filesystem check during MPI_File_open

[Rajeev Thakur]

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) <jsquyres at cisco.com> 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
> jsquyres at cisco.com
> For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
> 
> _______________________________________________
> discuss mailing list     discuss at mpich.org
> To manage subscription options or unsubscribe:
> https://lists.mpich.org/mailman/listinfo/discuss