SANs Get Wired for Long Distance

FC over wan can extend networks' reach, but more tests are needed.

For the most part, todays SANs have been limited to campus-size environments—a direct result of Fibre Channel technologys 10-km limitations. That may soon change.

Fibre Channel over WAN, the process of extending storage area networks over WAN links via Fibre Channel, promises to enable organizations to mirror data or run backups from a distant location. Therefore, its no surprise that Fibre Channel-over-WAN technology, which is becoming available now, would be an appealing option for businesses that cant afford to lose data.

However, like any technology thats just out of the think tank, Fibre Channel over WAN must be put through a trial by fire. eWeek Labs advises bleeding-edge IT departments that must have the fastest-possible solution to try these products with extreme caution; IT managers who want to implement them should do extensive testing before throwing this into a mission-critical SAN.

Although iSCSI may have a lock on expanding the range of WANs into low-end, short-range SANs, Fibre Channel over WAN will give it tight competition in the long-range SAN extension market.

Upstart companies including Akara Corp. and LightSand Communications Inc., for example, have introduced products that extend SANs over WANs without the latency created by IP.

Technologies that have to traverse WANs are expensive by nature compared with LAN technologies because its much more difficult to move data over thousands of kilometers than over shorter distances.

Fibre Channel-over-WAN technologies are not miracle workers; they cant make the process of pushing Fibre Channel storage traffic over a WAN an inexpensive process.

Optical links can cost several thousand dollars per month to lease, and a Fibre Channel-over-WAN solution wont make the optical link less expensive. However, it will allow IT managers to squeeze more data through those pipes when compared with FCIP (Fibre Channel-over-IP)- or iSCSI-based systems. The new Fibre Channel-over-WAN products typically have line interfaces that allow them to connect to everything from OC-3 to OC-48 cabling.

Fibre Channel-over-WAN technologies currently target larger companies (with presumably deeper pockets) that have either Fibre Channel or SONET (Synchronous Optical Network) connecting their disparate sites and need to replicate data and share backup resources over long distances.

We believe smaller companies will probably be best served by systems that use easily accessible IP links and tap either iSCSI or FCIP together with virtual private networks to link their SANs over WANs.

An Edge Over IP

The selling point that companies such as Akara and LightSand make is that because best-effort protocols such as IP are lossy and because IP links are generally oversubscribed, SANs that rely on general-purpose IP links will suffer performance hits.

Unlike iSCSI and FCIP-based systems, which are touted as long-range SAN solutions by companies including Computer Network Technology Corp., this new generation of Fibre Channel-over-WAN products can avoid IP packet loss and overhead by putting Fibre Channel traffic directly onto SONET links. (SONET is the physical-layer optical networking standard that is normally used to transmit IP packets over WANs.)

Products such as Akaras OUSP (Optical Utility Services Platform) 2000, which was released in the summer at a starting price of $20,000, can be plugged into SONET to transfer Fibre Channel traffic over thousands of kilometers of fiber-optic cable.

In demonstrations at the Storage Networking World trade show in San Jose, Calif., last month, we saw the Akara OUSP 2000s very high bandwidth priority capabilities in action and were impressed with its ability to carve up bandwidth.

Because boxes such as the OUSP 2000 will be connected directly into SANs, however, interoperability will be a major issue.

Akara has already been certified with big SAN vendors, including Brocade Communications Systems Inc., IBM and McData Corp., and is in the certification process with EMC Corp., Hewlett-Packard Co. and Hitachi Data Systems Corp.

Senior Analyst Henry Baltazar can be reached at