Optical networking drives enterprise storage area networks

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As the cost of higher bandwidth drops, demand for storage-area networking takes off.

Todd Bundy and Andrew Rowney,
ADVA Optical Networking

Optical networking has flourished for long-haul telecommunications networks, providing incredible amounts of bandwidth for a relatively low cost. The driver of this demand is the growth of Internet traffic, but the rate of increased demand is directly proportional to the cost reductions now available for the higher bandwidths.

Optical networking is creating the same phenomenon for storage-area-networking traffic. Today, storage area networks (SANs) are expanding, becoming accessible to more locations and requiring increasing bandwidth due to the lower cost and higher availability of optical networks. The two businesses-storage-area and optical networking-create cycles that directly benefit and stimulate each other (see Figure 1). Michael Ruettgers, CEO of storage-networking vendor EMC Corp., has noted this effect as a major driver for both the storage- and optical-networking industries.

Optical networking for storage applications began in the early 1990s. The Fortune 100, banks, insurance companies, and financial institutions had enormous multiterabit files in their mainframe networks that required connectivity and backup to remote locations. A special 200-Mbit/sec optical protocol, Escon, was the primary interface used for these mainframe applications. Th 0101lwspr10f1

Figure 1. The increased demand for storage-area networking over optical networks is a result of the lower cost of bandwidth.

Around the same time, EMC developed a way of moving and copying data between disk storage systems without the use of the mainframe. This method, called data mirroring, allowed for the offsite protection of critical data for later retrieval in the event of a major disruption of computer-processing capability. Tremendous cost savings were realized because of fewer processor requirements, and data backups and restores could be done as needed, not based on time windows when the mainframe was not in production use.

Connectivity between separate facilities was expensive, however. Wide-area-network (WAN) converters or gateways were needed to convert the mainframe data to a compatible SONET/SDH service in the form of T3/E3 (44.736 Mbits/sec) or OC-3/STM-1 (155.52 Mbits/sec). Not only was the conversion equipment expensive, the performance was often too slow and costly to justify widespread usage.

Several large enterprises were able to gain access to leased dark fiber to run their storage applications at native speeds, providing more than a four-fold improvement in performance for nearly the same cost. The first enterprise WDM systems were deployed in 1995 to multiply the capacity of the dark fiber and drastically reduce the cost per megabit. These enterprise WDM systems quickly grew from four to eight channels. In 1998, the first 16-channel DWDM systems were deployed, as evidenced by their use in EMC's own disaster-recovery network. Today, DWDM systems are widely deployed for use in SANs (see Figure 2). Th 0101lwspr10f2

Figure 2. Service providers today can use WDM systems to offer high-speed transparent optical-networking services with support for a wide range of optical interfaces for storage-area networking over an optical network.

In the past, the big issue for the network managers trying to meet the storage demands of large enterprises was getting access to private fiber. Most incumbent carriers would not lease dark fiber due to their lack of control for the services.

Metropolitan-area service providers started to seriously step into the game in 1998 by offering high-speed transparent optical-networking services (TONS). Telecommunications companies such as Bell Atlantic (now Verizon) and Colt Telecom began to support Escon, Fast Ethernet, and ATM (155-Mbit/sec) applications across a single TONS service for the price of a T3/E3.

Enterprises' bandwidth demand has increased as new and higher-speed interfaces have emerged. The small computer-systems interface (SCSI), used by most open-systems storage devices, has migrated from a copper interface to a 1-Gbit/sec Fibre Channel optical interface. Mainframe devices have migrated from Escon to gigabit fiber connection (Ficon), while Fast Ethernet backbones have been upgraded to Gigabit Ethernet in less than two years.Th 0101lwspr10f3

Figure 3. Reduced bandwidth cost is increasing the demand for storage-area networking over optical networks. Today, metropolitan service providers provision high-speed enterprise services at a leased-line cost near that of a traditional T3/E3 (44.736 Mbits/sec).

Today, service providers are targeting the demand for high-speed metropolitan applications with a more aggressive rollout of TONS. Verizon and Colt are now joined by British Telecom, MCI WorldCom, France Telecom, Bell South, and more than 20 other service providers. These providers are all deploying optical networking to provision high-speed enterprise metro services-everything from a 10-Mbit/sec Ethernet to a 1-Gigabit Ethernet to a 2.5-Gbit SONET/SDH-at a leased-line cost near that of a traditional T3/E3 (see Figure 3).

The equipment used to deploy a TONS service must meet several key criteria:

  • Support for point-to-point architectures and small metro rings.
  • Transparent channel modules with the ability to set bandwidth remotely through software.
  • "One-channel-module-does-all" design to reduce maintenance spares.
  • Channel speed range of 10 Mbits/sec to 2.5 Gbits/sec.
  • Up to 32 DWDM channels per fiber pair.
  • Up to 64 DWDM channels per 7-ft cabinet.
  • Optical link protection capability.
  • Hardware and link management through the network operations center.
  • Hot-swap for all assemblies.
  • Easy installation and maintenance.
  • Low power consumption.
  • High meantime before failure.

The technology developments leading to cost-effective optical-networking services have unlocked the enterprise barrier and created a new model for metropolitan area networks. Islands of isolated data-storage networks are no longer required and high-speed access to all data can be available everywhere. For many enterprises, this fundamental change will drive the storage network back to a centralized storage model, creating even greater demands for optical-networking services. Market researcher IDC predicts that storage management costs will consume 75% of a company's information-technology budget by 2003. Moving to a centralized storage-management model eliminates much of this cost.

Feeding on the opportunity created by the optical-networking boom, a new kind of outsourcing is emerging-the storage service provider (SSP). The SSP model allows large and medium-sized enterprises to fully outsource not only network connectivity, but also the entire SAN. The goal is to allow enterprises to focus on their business and have the SAN available to help manage that growth.

The SSP leverages high-performance bandwidth to connect multiple customer sites to a common data-center location. All data storage and disaster recovery can be provided by the SSP much more cost-effectively due to the efficiencies of scale and a centralized storage model.

"Many large enterprises and business park customers have been searching for a solution to manage and protect their storage networks, because [these companies] do not have the expertise or resources to support these networks themselves," states Thomas Hohendanner, managing director for TeraGate, a startup SSP. "Optical networking has enabled a storage service provider to create a very attractive offer for storage and network management-as simple as an electric utility."

While the costs of high-speed metro TONS services have plummeted in the past few years due to optical networking, many high-speed WAN services are also becoming more affordable, which is expanding SAN access beyond even the metro area. New WAN gateways are now available to convert 1-Gbit/sec Fibre Channel applications to 622-Mbit/sec ATM or 1.25-Gbit/sec Internet Protocol and transmit the data from those applications over the WAN. It is possible to envision regional and national SSPs within just a few years.

Optical networking has just started to unleash the bandwidth potential of the fiber-optic infrastructure. SANs are one of the key applications that will devour the bandwidth offered and further drive the industry toward more cost-effective optical-networking services.

Todd Bundy is director of business development in North America for ADVA Optical Networking (Ramsey, NJ). Andrew Rowney is global director of business development, storage networking. The company's headquarters is in Munich, Germany.

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