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Implementing Fibre Channel Over A Wide Network.

Storage is expanding--doubling and tripling--especially for the most successful companies, the Fortune 1000. Although this expansion is an indication of a bountiful business, it brings to light existing issues such as low disk capacity, inadequate tools, and thin staff. Business drivers compound the issue of data growth with the concurrent need for improved productivity and demands for constant uptime. Therefore, growing storage requirements and the demand for faster systems constantly challenges business continuity. Isolated storage systems in multiple locations are another obstacle to business continuity.

storage Area Networks And Fibre Channel

Storage Area Networks (SANs) link servers and storage to create a network of storage that removes heavy storage activity from the local area network (LAN). Fibre Channel is a networking protocol that provides high-performance channel and network data transfer. At first, SANs were isolated within the enterprise and storage systems were not considered mission-critical. Now, SANs face the same mission-critical requirement as transaction processing applications, including the requirement to support distributed operations.

Fibre Channel delivers more distance than SCSI, but not more than 10 kilometers or 6.2 miles, which is effective for campus and local SANs. However, applications such as disk mirroring and backup/restore demand greater distances. Now, Fibre Channel can be deployed over a Wide Area Network (WAN) to deliver these and other applications to the geographically distributed enterprise, but it has not been an easy road. This article explains the barriers to and approaches for implementing Fibre Channel over WAN (Fig.l).

Chief Barriers Of Fibre Channel Over WAN Implementation

The primary challenges in bringing Fibre Channel over WAN are the quality of service and the cost of bandwidth. Quality of service refers to response time and service continuity. Increased distances increase response time, which in turn degrades application performance. Furthermore, connections over long distances involve multiple carriers, increasing the risk of service disruption. Companies can combat low quality of service by employing high-speed communications links with multiple paths to destinations in the networking architecture, utilizing communications bandwidth effectively and employing reroute and altenate path techniques to minimize the impact of service disruptions. For Fibre Channel, channel extension techniques can be used to overcome distance and latency issues associated with wide area operations.

Due to limited availability, bandwidth costs have been the most significant cost in WAN structures, but communications costs are expected to follow the route of Moore's Law and significantly decrease in cost as infrastructure is made more readily available. Thousands of miles of cables are being laid. In addition, the telecommunication companies are migrating to multiple data services interlaced or multiplexed over the same fiber, which will increase capacity dramatically. Increased competition and blooming capacity will lower the price of bandwidth (both voice and data services) and make WAN structures, and the possibility of Fibre Channel over WAN, more affordable.

Another barrier is the lack of standards for Fibre Channel connectivity. At this time, at least 20 separate documents, each defining an aspect of Fibre Channel, are either proposed or in draft form. Connectivity technology can act as an intermediary while Fibre Channel standards evolve.

Suggested Implementation Phases Of Fibre Channel Over WAN

Today, companies can immediately take advantage of Fibre Channel over WAN technology by leveraging the products and services available that conform to current and proposed standards. Companies should consider a three-phase implementation of Fibre Channel over WAN to ensure full Fibre Channel compliance with standards as they become accepted. It is also important to work with vendors who have a proven reputation in storage networking and wide area connectivity.

* Phase One: Using the Fibre Channel Arbitrated Loop (FCAL) standard, extend server-to-storage connections over the WAN. Applications that will be available over the WAN include remote disk mirroring and tape vaulting for backup/restore.

* Phase Two: Create a switch-to-switch extension that allows the development of a "virtual fabric" with which physically remote locations can interconnect. This "virtual fabric" will enhance business continuance operations by providing the next level of protection against application failover for frameworks in different buildings, for example.

* Phase Three: Construct a full Fibre Channel Backbone (FC-BB) that will allow fabric-to-fabric interoperability regardless of vendor products and services that comprise the fabrics (Fig. 2).

Fibre Channel technology initially drove SANs to provide higher bandwidth, scalability, longer-distance connectivity, and resiliency, and Fibre Channel over WAN technology will enable companies to achieve significant business benefits by bridging the scattered islands of storage to create storage as a true resource.

Mark Knittel is the vice president of marketing for business development at Computer Network Technology (Minneapolis, MN).
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Title Annotation:Technology Information
Author:Knittel, Mark
Publication:Computer Technology Review
Date:Nov 1, 1999
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