[Pvfs2-users] how to set strip count and strip size

Phil Carns carns at mcs.anl.gov
Sat Mar 12 11:35:18 EST 2011


Hi,

The setfattr utility is available in the "attr" package in Debian.   
Here are some instructions for changing the default number of datafiles 
(ie, the strip count) for a directory:

    http://www.pvfs.org/fisheye/browse/PVFS/doc/pvfs2-tuning.tex?r=1.2#l160

And here are some instructions for changing the strip size:

    http://www.pvfs.org/fisheye/browse/PVFS/doc/pvfs2-tuning.tex?r=1.2#l227

That will only affect future files that are created in the directory; it 
doesn't modify any existing files.

Unfortunately, I don't think there is a good reference for how to select 
a strip size.  It depends on both your hardware and access patterns.

Most of the time there isn't much reason to change the dfile count.  It 
used to be helpful to lower it for directories containing small files, 
but the file stuffing optimizations in recent versions of PVFS take care 
of the most significant cases automatically now.  You might find some 
benefit to changing it for some special case workloads, but the default 
works pretty well for most people.

-Phil

On 03/11/2011 04:07 PM, Matthieu Dorier wrote:
> Hello,
>
> The PVFS documentation mentions the possibility to set the 
> distribution, and the parameters of this distribution (such as the 
> strip count and strip size), using setfattr. But it seems setfattr is 
> an external tool, not available on my platform (a Debian linux 2.6) 
> and I don't find it anywhere on the Internet. Is there any other way 
> to set these attributes for a given directory, using only what is 
> provided by PVFS?
>
> Also is there a study or a paper about the influence of such 
> parameters on the performance with respect to the I/O pattern of the 
> applications?
>
> Thank you,
>
> Matthieu Dorier
>
> -- 
> Matthieu Dorier
> ENS Cachan, antenne de Bretagne
> Département informatique et télécommunication
> http://perso.eleves.bretagne.ens-cachan.fr/~mdori307/wiki/ 
> <http://perso.eleves.bretagne.ens-cachan.fr/%7Emdori307/wiki/>
>
>
> _______________________________________________
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