[Pvfs2-users] Striping in PVFS2 on a per-file basis

[Rob Ross]

If the files are being created serially, you could use the "change the  
directory attributes" approach. Again, those attributes are only used  
at the time the file is created; if they are changed afterwards, they  
only impact files created after the change.

Might be easier to just use different directories for your different  
files...

Rob

On Jan 23, 2009, at 3:15 PM, FileSystem Novice wrote:

> Thanks for the clarification, Brad & Rob.
>
> Regarding the 3 ways suggested to accomplish this, the 2nd one  
> probably won't work for our system (when multiple files with  
> different distribution parameters need to be written onto the same  
> directory).
>
>
> On Fri, Jan 23, 2009 at 3:38 PM, Rob Ross <rross at mcs.anl.gov> wrote:
> On Jan 23, 2009, at 2:09 PM, Kyle Schochenmaier wrote:
>
> You are spot-on with your assesment of the striping in PVFS2.
> Each file gets a round-robin striping based on the distribution
> parameters of its directory.
> To my knowledge, you cannot set things on a per-file basis, as the
> distribution is done on a per-directory basis.
> If I'm wrong, everyone please feel free to flame me ;-)
>
> Distributions are defined on a per-file basis. The attributes on the  
> directory are used as hints on what distribution parameters to use  
> for files when they are created.
>
> There are at least three ways then to accomplish what you're  
> thinking of (different distributions for different files):
> - use MPI-IO and specify distribution parameters as hints; they will  
> be used to create the file with a specific distribution
> - change the attributes on the directory before you create a file,  
> so they match what you want
> - use pvfs2-cp "-s" and "-n" options to specify your desired  
> parameters, copy an empty file, then write your data into the file  
> with whatever app you like
>
> Rob
>
>