Clustered file system

[Rico Secada]

Hi

We are expanding at work and I am messing around with different setups.

I need a file system that will *look* like its just on one machine, 
like when mounting with NFS, but because of the large amount of data, 
I really need to expand the files to several servers.

Also I need some kind of security.

I haven't set something like this up before so all kind of friendly 
advice would be greatly appriciated. What solution is recommended?

Best regards
Rico