[Pw_forum] I/O performance on BG/P systems

[Paolo Giannozzi]

On Mar 29, 2011, at 9:49 , Gabriele Sclauzero wrote:

> Are you referring to the wf_collect feature?

yes

> I've not been using that, so I was supposing that each process
> writes independently its piece of wavefunctions (at least for PWscf),
> am I right?

you are

> Do you think that this might be a symptom of a GPFS problem or
> misconfiguration?

not sure

> I've tried to used disk_io='low' in some relax calculations, this  
> might
> be a good compromise.

as long as you have sufficient memory to keep wavefunctions into RAM,
this is the best solution

> However the code writes the wavefunctions only once at the end of  
> the run.
> Wouldn't it be more reasonable to write them at the end of each  
> ionic step?gh
> (just a personal opinion...)

it is not always possible to listen to all opinions...this behavior  
is easy to
change, though: look for io_level in PW/electrons.f90

P.
---
Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222