A LOT HAS CHANGED since 2000 when EMC announced HighRoad, a high-performance add-on for its Celerra NAS platform. But until last month, the product, also known as Multi-Path File System (MPFS), hadn't changed much at all, and it appears never to have made a strong showing in the marketplace.
But in a tip of the hat to Ethernet's growing pervasiveness in the data center, EMC has launched an iSCSI version of HighRoad named MPFSi. "There are a lot of sites out there that don't have a Fibre Channel [FC] infrastructure, for example, ISPs," says Ken Steinhardt, EMC's director of technology analysis. However, faster file serving than what straight Celerra can give them may still be needed.
With the new MPFSi, file requests are passed to Celerra via NFS but, depending on the data being requested, they're passed back with either NFS or iSCSI, for up to four times the performance, says Steinhardt. In contrast, the original MPFS passes block data back over FC or SCSI.
"It's a classic case of separating out the data path from the control path," says Arun Taneja, founder, president and consulting analyst at Taneja Group, Hopkinton, MA. For environments dealing with large files, this approach makes a difference. "Moving data over an IP network is never as fast as shipping blocks over Fibre Channel--or blocks over IP," he says.
In other respects, HighRoad and MPFSi are similar, both opting to pass back blocks, and both requiring a file-system driver to be loaded on the client machine.
High-performance NAS player Panasas, Fremont, CA, takes an approach similar to that of HighRoad to turbocharge its file serving. Panasas users can access the ActiveScale Storage Cluster with NFS or can load its proprietary DirectFlow driver on clients to allow them to accept data via parallel data streams. The major difference between the EMC and Panasas approach is that MPFSi relies on iSCSI, whereas Panasas relies on a proprietary, object-based protocol.
Going forward, the idea exemplified by MPFSi and DirectFlow could be standardized into the NFS protocol, says Larry Jones, Panasas' VP of marketing. Several members of the Internet Engineering Task Force (IETF) NFS v4 working group, including EMC, Network Appliance (NetApp), Panasas and Sun Microsystems, have been involved in a subcommittee on parallel NFS implementations, reports Jones.
But for now, some more-established NAS vendors dispute the premise that serving files via blocks is faster than NFS. "It's a question of configuration and packet size," says Rich Clifton, NetApp's VP and GM of the network storage business unit. Done right, "I think they're close," he says.