Acopia has launched a multi-site virtual network-attached storage product. The product comes as an update to the software in its ARX switches. This range of switches supports remote offices and data centres. A switch presents a set of network-attached storage (NAS) devices as a single virtual NAS resource with files movable between the individual boxes for load-balancing purposes.

Rainfinity also virtualises NAS boxes. A spokesperson said Rainfinity had had a multi-site capability for a while.

As with virtualised disk storage in SANs, NAS virtualisation is a foundation for other services such as replication, migration and tiered storage such as Fibre Channel and SATA drives. By adding the multi-site capability through a global namespace, central and remote sites can share the same virtual NAS capability. This aids storage consolidation and management. It also brings virtual NAS into conflict with WAFS - wide area file systems - products such as those from Tacit Networks and Riverbed.

In both cases servers in remote sites see what appear to be locally-attached files via NFS (Unix) or CIFS (Windows) protocols.

There is no logical reason why a WAFS product couldn't extend a NAS device to remote sites, although it wouldn't virtualise NAS devices. Remote users would see the NAS files they had access to but the central IT staff wouldn't have the load-balancing, storage utilisation and replication features a virtual NAS product brings.

Wide area virtual NAS products, like those from Acopia and Riverbed, don't have the network acceleration technologies exhibited by WAFS products, although they may well use some of them, such as file compression. Remote users get access to the virtual NAS files but more slowly than if WAFs technology was to be used. Consequently, a convergence of WAFS and virtual NAS products, both using in-band switch hardware, is both a necessity and bound to happen.

It also seems logical that NAS product suppliers could incorporate either virtual NAS technology or WAFS technology or both into their products. This would be similar to the way that Sun and Hitachi are incorporating SAN storage virtualisation technology into drive array controllers such as Sun's 6920 and HDS' NSC55.