pnetcdf and pNFS?

[Rob Ross]

Never used it. We don't have convenient access to a pNFS installation.  
-- Rob

On Jul 26, 2010, at 4:39 PM, Michalakes, John wrote:

> Thanks Rob. I don't think we rely on any read/write access, but I'll  
> have to ponder.  Assuming that's the case and that we're doing only  
> read-only or write-only to a given file, have you found that pNetCDF  
> on pNFS is reasonably fast and scalable (relative to other parallel  
> file systems)?  Thanks, -John
>
> -----Original Message-----
> From: Rob Ross [mailto:rross at mcs.anl.gov]
> Sent: Monday, July 26, 2010 3:27 PM
> To: Michalakes, John
> Cc: parallel-netcdf at mcs.anl.gov
> Subject: Re: pnetcdf and pNFS?
>
> The short answer is that I think it should be ok if you are doing  
> read-
> only or write-only access.
>
> pNFS is NFSv4, which by default has close-to-open semantics as I
> understand it. However, the NFSv4 standard writers were careful to
> make sure that clients would not inadvertently touch bytes they
> shouldn't when writing (i.e., not touch bytes that weren't written via
> R/M/W).
>
> close-to-open semantics mean that clients aren't guaranteed to see
> changes to the file that occur between an open and a close. Thus read/
> write access results are probably undefined.
>
> If someone knows better, I'm happy to be corrected!
>
> Rob
>
> On Jul 26, 2010, at 12:43 PM, Michalakes, John wrote:
>
>> Hi,
>>
>> Wondering if you have any information on suitability of pNFS for use
>> with pNetCDF?
>>
>> Thanks,
>>
>> John
>>
>> John Michalakes
>> National Renewable Energy Laboratory
>> 1617 Cole Blvd.
>> Golden, Colorado 80401
>> Phone: 303-275-4297
>> Fax: 303-275-4091
>> John.Michalakes at nrel.gov
>>
>