[Lustre-discuss] mpi-io support

[Marty Barnaby]

To return to this discussion, in recent testing, I have found that 
writing to a Lustre FS via a higher level library, like PNetCDF, fails 
because the default for value for romio_ds_write is not disable. This is 
set in the mpich code in the file /src/mpi/romio/adio/common/ad_hints.c

I believe it has something to do with locking issues. I'm not sure how 
best to handle this, I'd prefer the data sieving default be disable, 
though I don't know all the implications there. Maybe an ad_lustre_open 
should be a place where the  _ds_  hints are set to disable.

Marty Barnaby


Weikuan Yu wrote:
> Andreas Dilger wrote:
>   
>> On Mar 11, 2008  16:10 -0600, Marty Barnaby wrote:
>>     
>>> I'm not actually sure what ROMIO abstract device the multiple CFS
>>> deployments I utilize were defined with. Probably just UFS, or maybe NFS.
>>> Did you have a recommended option yourself.
>>>       
>> The UFS driver is the one used for Lustre if no other one exists.
>>
>>     
>>> Besides the fact that most of the adio that were created over the years are
>>> completely obsolete and could be cleaned from ROMIO, what will the new one
>>> for Lustre offer? Particularly with respect to controls via the lfs utility
>>> that I can  already get?
>>>       
>> There is improved collective IO that aligns the IO on Lustre stripe
>> boundaries.  Also the hints given to the MPIIO layer (before open,
>> not after) result in lustre picking a better stripe count/size.
>>
>>     
>
> In addition, the one integrated into MPICH2-1.0.7 contains direct I/O
> support. Lockless I/O support was purged out due into my lack of
> confidence in low-level file system support. But it can be revived when
> possible.
>
> --
> Weikuan Yu <+> 1-865-574-7990
> http://ft.ornl.gov/~wyu/
>
>   

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