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





On Jan 16, 2009, at 16:12, "Ramiro Blanco" <ramiblanco gmail com> wrote:

2009/1/13 Steven

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.

I think Steven's referring to the creation of many small files in a dir.
The issue at play is that the node must grab a write lock on the directory inode in order to add a dentry.

The same thing applies to other dentry changes. If you're only modifying inodes, and not the dentries themselves, you can focus your tuning efforts elsewhere.

Hth,
-paul


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