Server :: Read Write Priority Samba Nfs

I have an HP GL380 with an MSA20 connected for storage space, we use it as an nas unit. The system is SLES 10. We use both NFS and SMB for file sharing, no special users and so. We are 8-10 users of the machine. We store both large and small files such at thumbnails and disk images.

Now, my problem. I�d like to give more priority for reading files on the server, so a user can look at pictures without problem, and if another user is writing an image file of an disk (10-1000 GB) this writing process should get less priority. The most important is always reading files, to get the job done.