[mpich-discuss] ROMIO hints start_iodevice, striping_unit, and striping_factor

[Wei-keng Liao]

Hi,

I found the ROMIO hint start_iodevice appears in ad_pvfs/ad_pvfs_open.c,
but is not defined in include/adioi.h. So, this hint is ignored by  
ROMIO.
Can I suggest to add this to ADIOI_Hints_struct?

Two other hints, striping_unit and striping_factor, are defined but  
currently
are only set by taking user's inputs. None of the ADIO drivers, except  
PVFS-1,
sets these hints by querying the file system. It would be nice to see  
PVFS-2,
Lustre, and GPFS (BGL) with this implemented, so users can query a  
file's
striping info through MPI_File_get_info(). In addition, file domain  
alignment
depends on the value striping_unit. It is important to detect this value
automatically.

One approach to add this functionality is to query the stripe info in
ADIOI_xxx_Open by process fd->hints->ranklist[0] and broadcast it to  
the rest
of processes (including cb_nodes and non-cb_nodes). The broadcast can  
be done
in ADIO_Open() in ad_open.c

Wei-keng