Re: [bgl-discuss] RE: [bgl-support #151] buffering

[Kamil Iskra <iskra@xxxxxxxxxxx>]

On Mon, Dec 04, 2006 at 15:46:19 -0600, Ray Loy wrote:

> > I am not sure I asked this already, but are the reads/writes buffered
> > on the Blue Gene ?
> no, unless you count going through the IO node (see copy below).
> maybe someone on bgl-discuss will have more details.

Correct; there is no explicit caching/buffering.  The NFS client running on
the I/O node might do some caching, but it won't be efficient.  PVFS
definitely does not do any caching, so if your application expects some, it
will be slow.

So you invoke UNIX read/write routines directly?  What is your request size
per call, on average?

Kamil

-- 
Kamil Iskra, PhD
Argonne National Laboratory, Mathematics and Computer Science Division
9700 South Cass Avenue, Building 221, Argonne, IL 60439, USA
phone: +1-630-252-7197  fax: +1-630-252-5986

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