Storage specifications are starting to emerge that may make it easier for IT managers to assemble and install their own storage-area networks and network-attached storage.
Fabric Shortest Path First (FSPF) and Direct Access File Specification (DAFS) are the first standards that let different vendors’ Fibre Channel switches interoperate and let data be delivered faster from applications. Analysts say the standards will make it possible for users to design, install and implement SANs and NAS from components instead of buying turnkey packages from vendors.
To advance interoperability, individual storage and system vendors have also set up interoperability labs to test storage switches, hubs, host bus adapters and disk arrays with their own equipment. EMC Corp., StorageTek, Brocade Communications Systems Inc. and Compaq Computer Corp. are among those participating. While the labs are focused on proving interoperability between the vendors’ storage equipment and other devices, none of the labs are open to testing any server operating system with any storage device that has an interconnected router or switch.
“Standards are very important to us, period,” says a storage resource manager for a large retailer in the Southern U.S. who asked not to be named. “From a buying standpoint, we realize that standards are not going to be in place in time for us, and [our company] is going to go ahead with SANs knowing that whoever we go with today will be proprietary. In the future, [the market] will open up so we can realize our goal of putting together a plug-and-play SAN.”
FSPF is the result of a collaboration between Brocade, Gadzoox, McData, Ancor and Vixel to make their switches work together. Similar to the Open Shortest Path First protocol used by most IP router vendors, FSPF lets routing tables act as maps for routing traffic through the network in the most efficient manner. The protocol was submitted to the ANSI earlier this year. FSPF should be codified into a standard by year-end. Brocade has implemented FSPF in its SilkWorm switches, and other switch manufacturers will include it in their products by year-end.
DAFS is a high-level protocol for file-by-file transfer of data across the network directly between client and storage memory. Use of the protocol will increase the speed of the network and relieve the system CPU of processing overhead, especially in hungry database and multimedia applications. It is based on the Virtual Interface Architecture designed by Microsoft, Compaq and IBM, and is independent of the Ethernet or Fibre Channel protocol and media that is used.
Network Appliance, Seagate Technologies and Intel drafted the DAFS proposal. DAFS will ultimately replace the Network File System (NFS) protocol used by NAS devices. Users should see the first implementations of DAFS-compliant NAS devices by the middle of next year.
“DAFS is simply providing a better mechanism than NFS for NAS file service,” says Steve Duplessie, an analyst with Enterprise Storage Group in Milford, Mass. “Standards like DAFS and FSPF give us one way to do something without learning something new each time we buy a product. For instance, if I know how to zone a Brocade switch, I know how to zone a Vixel switch.”
Both protocols, while speeding the data network and making it more manageable and interoperable, don’t cover interoperability issues that are necessary for SAN and NAS operation. Neither protocol addresses the switches exchange of storage array zoning or partitioning information, how devices join the network or which switch becomes the principal switch on the network and thus is in control of data exchanges. There is also no way to identify a distributed name server or how domain ID assignment takes place. The Fibre Channel Industry Association is working on these issues.
