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

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).

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

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,

Ramiro Blanco

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