Optical networking is the link to global SANs

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Massive data demand will require enterprises to connect their storage area networks to optical carrier backbones using lambda switch routers.

Kanwar J.S. Chadha, Ph.D., Entrada Networks Inc.

While George Gilder and others are extolling the virtues of all-optical networks and unlimited bandwidth, all is not well in the world of optical networking. Some voices within the service-provider community are very concerned about a bandwidth glut, despite the accelerating pace of innovation, eager optical entrepreneurs, and supportive capital markets.

Service providers have incurred billions of dollars in debt to build networks worldwide; however, there are not enough applications to soak up all of the available bandwidth. As a recent Wall Street Journal article, "Operators of Fiber-Optic Networks Face Capacity Glut, Falling Prices," (October 19, 2000) notes, this situation has put executives such as Greg Maffei, president and CEO of 360networks, in a challenging position. To service their debt and maintain investors' confidence, companies such as 360networks must fill these fat pipes with bandwidth-intensive services as quickly as possible.

For the optical-networking industry, the time is certainly fortuitous for the introduction of storage-area-network (SAN) transport technology. Extending SANs beyond their current limitations of local fabrics will enable remote applications that drive massive amounts of traffic through optical networks.

Back-end networks connecting storage devices via peripheral channels such as Fibre Channel are quickly emerging as the preferred solution for storing and providing instant access to mission-critical information. Known as SANs, these networks provide an easier way to expand storage capacity and improve data sharing and access. SANs help enterprises create locally shared storage systems consisting of multiple hosts accessing data on the same spindle. By facilitating data sharing in a heterogeneous environment, SANs enable central data management and performance measurement.Th Acf668

Storage-area-network (SAN) lambda switch routers have the potential to serve as a bridge between Fibre Channel-based SAN traffic and the optical carrier backbone. That communication today requires several devices such as Internet Protocol routers and director-level switches.

These compelling benefits are driving rapid adoption of SAN technology. Dataquest expects the SAN market to reach $1.8 billion by 2002. The 21% of the external storage market-storage capacity outside of disk drives built into servers-currently held by SANs is estimated to grow to 70% by 2003.

In the geographically dispersed enterprise, however, disparate SANs could hinder the performance of mission-critical applications such as remote disk mirroring and real-time data archiving, if these storage networks do not provide sufficient guarantees to meet the demands of 24x7 global e-commerce.

To optimize performance, local SAN fabrics now need to be extended across high-speed communications links to create a fully integrated global SAN fabric that makes mission-critical information available enterprise-wide, even when that enterprise spans the world.

A key enabler of global SANs, optical technology has the power to extend virtually any remote SAN to the end user by creating direct, big-bandwidth, optical SAN-to-SAN connections. Optical networks, such as those owned and operated by 360networks, can connect disparate islands of SANs reliably and with low latency. When SAN traffic moves beyond the edge of the enterprise, 360networks will be able to feed its big-bandwidth pipes with a massive stream of terabits. Moreover, providers can take comfort in the fact that this stream will expand exponentially every year.

Achieving a low-latency global SAN will necessitate the integration of optical networking at the device level to provide a seamless interface to the big-bandwidth fiber-optic carrier backbone. Passive optical systems such as those found in many metro DWDM systems are inherently transparent to data format and speeds, ultra-scalable, and able to transport and add/drop traffic within the all-optical domain. Therefore, optical-networking technology is the ideal conduit for seamlessly delivering SAN traffic through communication networks.

Most current efforts to extend local SANs focus on interoperability between director-level switches and DWDM transport systems within the wide-area optical network. In this scheme, Fibre Channel SAN traffic is routed and mapped into directors where it is switched onto DWDM-based light paths for long-distance transport to directors and routing devices at destination points, in essence, creating SAN-packed wavelengths over carrier backbones.

This approach has the potential to create wide-area storage networks that exhibit low latency once storage traffic reaches the WAN. However, it also accentuates and pushes the SAN-traffic bottleneck to the edge of the storage network-the point of pain that optical SAN switching can alleviate.

All-optical SAN switch routers have the potential to efficiently bridge the "language barrier" between Fibre Channel-based SAN traffic and the carrier backbone. Making the two worlds communicate now requires a plethora of translation devices-Internet Protocol (IP) routers and director-level switches-that may add to network complexity and create bottlenecks (see Figure).

With a SAN lambda switch router, such as Fibre Channel to IP to light, conversions are eliminated and the two worlds are bridged. A common SAN-to-public-backbone language is achieved. These devices have the potential to deliver massive savings in equipment, and by eliminating electrical-to-optical conversions, the SAN Lambda switch router will enable super-efficient native Fibre Channel-over-light transport.

These devices will also be key enablers of the nascent storage service provider (SSP) industry. SSPs offer outsourced storage on a pay-per-use basis. Improving the performance and extending the reach of SSPs will free fast-growing businesses from having to spend increasing amounts on storage systems and expensive, hard-to-find IT professionals. SSPs will evolve into global storage networks, which provide the same benefits as existing local SANs with more scalability and less risk.

Optical SAN transport is the linchpin in a global SAN environment that allows near-real-time storage applications and "always on" access to mission-critical information. Of course, deployment of wide-area storage networks will require more than just the integration of optical-switching technology. A common-carrier network optimized for data and storage management systems that differentiate local and remote resources is also needed.

As these technologies mature, the internetworking of isolated islands of SANs will result in efficient and reliable wide-area storage networks that provide long-distance backup, disaster recovery, and remote mirroring and recovery over significant distances. Transporting SANs beyond the local SAN fabric will greatly enhance data availability and allow enterprises to optimally locate data centers.

A global SAN fabric will enable many key application and business processes. SAN transport can ensure that precious data is protected and available when a natural disaster or major network disruption strikes. Data availability is a critical issue in the age of e-commerce since, for example, an online brokerage can lose millions of dollars if confronted with a single hour of data downtime. Linking SANs over the optical WAN allows for the replication of multihundred-gigabyte databases and guarantees 24x7 online availability.

Managing disk capacity, mirroring data sets, and backing up systems requires an army of costly storage professionals. Extending SAN fabrics will help equip SSPs to offer these and other storage services from central locations.

Today, replicating large data sets over long distances requires constant shipping of tape volumes via expensive overnight delivery services or transmitting data over slow and costly WANs. As SANs are linked over a fiber backbone, these locations become "transparent" to local users, enabling high-speed, high-volume data movement.

Companies providing online data access to global trading partners often have no time offline for backup. Rather than mirror data sets or implement complex software, large companies can simply outsource the process to external or internal SSPs that handle backup, volume management, and vaulting.

Effective supply-chain integration means sharing forecasting, inventory, and logistics data with suppliers and customers. Global SAN fabrics will route data from partner to partner across the high-speed fiber backbone.

Enterprise-wide access to stored information, currently a competitive advantage, is fast becoming a necessity. In other words, local SANs have to break the bounds of the campus.

Extending SAN fabrics globally requires optical switches and routers that seamlessly link SANs to the optical WAN. As SAN transport devices proliferate, storage traffic will fill currently under-utilized fiber-optic networks.

Nervous backbone service providers: hold tight. SAN transport will fulfill the tremendous potential of the fiber-optic backbone and allow globally dispersed enterprises to access and utilize information as never before.

Kanwar J.S. Chadha, Ph.D., is president and CEO of Entrada Networks Inc. (San Diego).

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