On Friday, September 23, 2011 05:17:01 AM you wrote:
> Hi all,
> 
>   Due to a certain app requeriments, I need to share an iscsi lun 
> between two sl5.x and five sl6.x servers. This lun is formatted with 
> ext4 fileysytem (I have used one of the sl5.x servers to do this). Can I 
> expect some type of problems ???

You need to reconsider the filesystem type for a shared LUN.  Even if only one server at a time mounts this filesystem, using a clustered filesystem will prevent some of the problems you might experience.  

See https://secure.wikimedia.org/wikipedia/en/wiki/Shared_disk_file_system for a list of filesystems providing this functionality; upstream's GFS is available, as far as I know, in both 5.x and 6.x and may be a good choice for what you're wanting to do.