NAS server setup questions

Hello,

We have a couple of old Dell PowerEdge servers with Dual Pentiums with 1
GB RAM and 4 160GB RAID disks. We don't know what type of RAID disks
are on this system though.

I would like to setup a NAS server using both the machines as one NAS
server. Is there any tutorial on how to setup a NAS server? I am
familiar with NFS but I recently heard of OpenFiler as a NAS solution.
Is this the only open source NAS solution?

Any information/pointers/advice is appreciated.

Thank you in advance.

NJ