[Pvfs2-developers] Sys create setting the datafile nodes depending on interface call.

[Walter B. Ligon III]

I agree.  I'm not completely clear what is being proposed, but it sounds 
to me like its more of a hint than a fixed parameter.  In any event, I 
think we should consider a well-designed PVFS hints mechanism that 
allows greater flexibility to be added for experimentation and even 
permanent use.

Walt

Rob Ross wrote:
> We should think about whether we really want these new parameters to be 
> optional (and thus *hints*) or mandatory (and thus new parameters), but 
> I do like the idea of providing a clean way to get extensions into the 
> calls for research purposes like this.
> 
> Rob
> 
> Murali Vilayannur wrote:
> 
>> Hi Julian,
>>
>>> Yes they are, but if we extend the system interface then we could 
>>> easily add
>>> another parameter if necessary and pending changes to the system 
>>> interfaces
>>> can be done in one modification. Thats why I was asking.
>>
>>
>> Ok, if you say so :).
>> I suppose if everybody agrees to this interface change do
>> send a patch ;)!
>>
>>>> Can you tell us what exactly was the problem with the new distribution?
>>>
>>> I was thinking that all distributions could benefit from such a 
>>> mechanism.
>>> Maybe the metatdata server for that file could be selected on the 
>>> same way,
>>> too ?
>>> Within the distribution itself the server names are not available I 
>>> guess, so
>>> there has to be some hack code outside. Also, I think due to dynamic
>>> migration etc. it is no good idea to write a distribution which 
>>> fixated the
>>> datafiles.
>>
>>
>>> This might be possible and is a another cool way, however we want the 
>>> user to
>>> set it for example with MPI_hints before the file is opened and only 
>>> to set
>>> it for a single file. For example somehow to use dedicated servers 
>>> for this
>>> file of a single file system, this might be used to place the 
>>> datafiles on
>>> the same nodes if the client also acts as a server or to place the
>>> datafiles "close" to the client on a dataserver. It seems to be rather
>>> inefficent to change the extended attributes of a directory then 
>>> create the
>>> file and change it back.
>>
>>
>> I am not sure how many people are going to use or require this
>> feature. I really wish we could come up with something cleaner though.
>>
>> Perhaps, we can create a new structure like PVFS_hints (that groups all
>> these extra parameters as they come by) and pass an optional
>> pointer to that at the time of sys_create, sys_mkdir and sys_symlink()?
>> thanks,
>> Murali
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-- 
Dr. Walter B. Ligon III
Associate Professor
ECE Department
Clemson University