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Re: [Linux-cluster] GFS2 tuning recommendations on RHEL 5.3



On Fri, 2009-01-16 at 19:12 -0200, Ramiro Blanco wrote:
> 2009/1/13 Steven Whitehouse <swhiteho redhat com>
>         Ideally you want to arrange the application so that you are
>         not pushing
>         the cache from node to node too often. So it depends on the
>         application
>         rather than the filesystem.
> All my nodes are all accesing the same data, as they are serving a
> moodle platform and a squirrelmail, so they _read_  all the same (i
> guess this is not an issue because they only read). 
> 
Yes, in fact thats pretty much the best possible case.

> 
>         The classic example is running a mail server
>         with lots of small files in the same directory, and the
>         solution is to
>         have a number of separate directories. The issue in that case
>         is that
>         creating and deleting files requires exclusive access to the
>         directory
>         in which the files are being created and deleted and thus the
>         application has to lay out its files such that all the nodes
>         are not all
>         trying to do that in just one single directory at once.
> So, you mean that when a node wants to write to a file locks the whole
> dir? In that case i would have a problem there because moodle saves
> lots (eventually thousands) of session files on a single dir
> 
Yes. Ideally you'd want to break up that dir into smaller ones. You
might still be ok depending on the rate at which the files are being
written, but be aware that this might be slow.

> 
>         It can make a huge difference to performance, and its not
>         something
>         which can really be fixed at a filesystem level,
> I guess i would have to split that session dir in several dirs if
> that's the case.
> 
> Thank you,
> 
Yes, thats the best thing to do if the application allows that,

Steve.

> 
> -- 
> Ramiro Blanco
> --
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> Linux-cluster redhat com
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