xternal / Network Storage Solution Needed for Xserve

We are likely soon purchasing a new Xserve system for directory services and are interested in an integrated or semi-integrated storage solution of some sort. Looking for something in the range of 1 TB RAID5 redundant disk space. Ideally this would be somehow connected to/with access managed by Open Directory.

Not looking to spend Xserve RAID type money, but I wasn’t sure if there are any NAS or similar type solutions out there to satisfy just storage needs, but will still provide some simple authenticated access, permissions management, etc. Something that will smoothly integrate into an OS X server environment.

Any thoughts or suggestions or anything I can clarify in my posting?

Thanks in advance.