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

[Rob Ross]

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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