[Linux-cluster] GFS2 tuning recommendations on RHEL 5.3

[Paul Morgan]

On Jan 16, 2009, at 16:12, "Ramiro Blanco" <ramiblanco at 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