[Lustre-devel] Control file striping

[Ben Evans]

Have you considered using a combination of OST Pools and striping fit
your needs?

-----Original Message-----
From: lustre-devel-bounces at lists.lustre.org
[mailto:lustre-devel-bounces at lists.lustre.org] On Behalf Of Atchley,
Scott
Sent: Monday, November 05, 2012 12:47 PM
To: Kalyana C
Cc: lustre-devel at lists.lustre.org
Subject: Re: [Lustre-devel] Control file striping

On Nov 3, 2012, at 1:41 PM, Kalyana C <ckkccf at gmail.com> wrote:

> Hello,
> 
> I am trying to figure out a way to:
> 
> set striping across a set of OSTs of my choice. 
> 
> lfs setstripe command and API call does not allow for this currently.
The user can only set the starting OST through the index parameter. I
appreciate why there is no such feature currently; you do not want to
let the users have control on how OSTs are used since it can result in
OST usage imbalance. 
> 
> However, I do have a valid usage case for such a feature and I am
trying to figure out the best way to do it. 

I have a valid use for it as well. It would be nice to have this feature
back.

Scott

> 
> One way to achieve the same result is through the use of OST pools.
However, the userland tools do not work from a client node, it has to be
run on the MGS. There are also other restrictions as described here:
http://wiki.lustre.org/index.php/Creating_and_Managing_OST_Pools
> 
> I am also digging through the Lustre source and header files to see if
there are other (undocumented) ways to do this. 
> 
> So, my questions are as follows:
> 
> 1) Is there currently a way for a user to control the striping of a
file / directory on a selected set of OSTs? If yes, is it possible to do
it through an API call or a command line utility?
> 
> 2) If answer to (1) is No, Is there a way to do this with admin rights
from the MDS or client nodes? 
> 
> 3) If pools are the only way to achieve this, is there an API call to
create, manage and destroy pools from a user application? Is there any
impact on performance of MDS components if pools are dynamically created
and deleted on demand? Can the API be called from a client node (root or
user) or does it have to be on the MGS?
> 
> Thank you.
> 
> Regards,
> Kalyana Chadalavada 
> 
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> Lustre-devel at lists.lustre.org
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