If you are considering any kind of SAN or NAS check out IPStor software by FalconStor.
IPStor can be loaded on two Linux servers. These servers communicate with eachother and will failover automatically. They communicate via fibre channel or SCSI with storage devices (RAID cabinets, tape libraries, etc). They communicate with other servers (NT, Linux, Win2k, Solaris) through a client/driver and a proprietary protocol over IP that virtualizes a SCSI adapter to the OS. That is, the OS sees a SCSI adapter, but in reality, this goes through to the IPStor boxes via IP and then on to the hardware storage devices.
Ahhh… but this gets better. Because this is all virtualized, the IPStor boxes can do cool stuff like provide mirroring, replication, snapshots, and easier backup/restore. IPStor can also function as a NAS device, so *NIX and Windows clients can use the storage directly. Oh… and drumroll… you can do full image replication over a WAN. So very cool.