[Pvfs2-developers] Distribution by hostname

[Walter B. Ligon III]

So, the plan is to put all of the hints in one long string and just pass 
that string in through the create interface?

Walt

Julian Martin Kunkel wrote:
> Hi,
> 
>>So I think we're mostly trying to work out what our API should really 
>>be, whether we should extend the distro functionality vs. going totally 
>>to hints, and if we go to hints what that API should look like, right?
> 
> probably the distribution needs a function which initializes/sets the internal 
> parameter depending on the string. Maybe another one which fancy writes the 
> parameters to a char buffer.
> 
> 
>>I'm down with that.  For the record, my concern over strings isn't in
>>our processing them - its the users having to muck with them -
>>especially when passing numeric data.  I just worry about lots of
>>mallocing/string copying blech when all you really want to do is set the
>>stripe size to the variable x.
> 
> I think extra mallocing is not really necessary only once to generate the 
> string which can be generated with snprintf  the string could look 
> like "ioservercount=2;ioservers=node1,node4;dist=simplestripe;dist_stripesize=65536"
> whereas options without the prefix "dist_" may be processed by code common to 
> all distributions. 
> 
> I do not see the benefit of putting the responsibility of server mapping to 
> the distribution right now (maybe for raid ?). I like outsourced/common 
> processing which is done in the create sm right now.
> 
> 
>>I personally don't think the environment variable approach is all that 
>>useful for PVFS. I believe this because there are only a *very* limited 
>>number of cases where it would apply cleanly (e.g. pvfs2-cp) that there 
>>isn't another mechanism for doing the same thing (e.g. MPI-IO hints). I 
>>think that MPI-IO hints should have some mechanism along those lines, 
>>and I wouldn't mind discussing that separately, but that's a different 
>>topic.
> 
> Ok I think its true that it might not be that useful for the common case and 
> that MPI hints should be used. 
> I found it useful for testing and experimenting with PVFS and I think its no 
> big deal if environment processing will not be added to CVS. I will add the 
> functionality fitting to the new hint interface in my branch.
> 
> I don't think that I actually might be useful for implementing the new hint 
> mechanism because I think you have to revise the code anyway (and it won't be 
> so much work I guess, either), but that is no big deal. 
> 
> Julian
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-- 
Dr. Walter B. Ligon III
Associate Professor
ECE Department
Clemson University