[Beowulf] network filesystem

[Robert Latham]

On Mon, Mar 05, 2007 at 04:26:28PM +0000, John Hearns wrote:
> That leads me to a damn stupid question - how do NFSv4 and ROMIO 
> interoperate then? Anyone got experience of that,
> or is it signed "There be Dragons" ?

It's not a stupid question at all.  It's very important to understand
the impact the choice of file system has on the higher levels of the
I/O software stack.

ROMIO does not have a special "NFSv4" ADIO driver.  ROMIO treats it
like regular NFSv3.  In short, you can use it, but you'll have to
disable all caching to make it behave correctly.  You'll get rather
bad performance for most workloads, but what good is fast I/O if you
get garbled data in your file?

I know I beat this drum a lot, but do consider a true parallel file
system like PVFS for your MPI-IO applications.   GPFS and Luster would
be good options too.  

==rob

-- 
Rob Latham
Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
Argonne National Lab, IL USA                 B29D F333 664A 4280 315B