Dell Brocade G620 Brocade 8.0.1 Fabric OS Administratiors Guide - Page 483
Managing Long-Distance Fabrics, Long-distance fabrics overview, Extended Fabrics device limitations
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Managing Long-Distance Fabrics ∙ Long-distance fabrics overview...483 ∙ Extended Fabrics device limitations...483 ∙ Long-distance link modes...484 ∙ Configuring an extended ISL...484 ∙ Forward error correction on long-distance links...486 Long-distance fabrics overview The most effective configuration for implementing long-distance SAN fabrics is to deploy Fibre Channel switches at each location in the SAN. Each switch handles local interconnectivity and multiplexes traffic across long-distance dark fiber or wave-length division multiplexing (WDM) links, while the Brocade Extended Fabrics software enables SAN management over long distances. Brocade Extended Fabrics is an optional licensed feature for Brocade SAN deployment over distances beyond 10 km. A Brocade Extended Fabrics license is required before you can implement long-distance dynamic (LD) and long-distance static (LS) distance levels. The LD and LS settings are necessary to achieve maximum performance results over inter-switch links (ISLs) that are greater than 10 km. For details about obtaining and installing licensed features, refer to the Fabric OS Software Licensing Guide. The Extended Fabrics feature enables the following functionality: ∙ Fabric interconnectivity over Fibre Channel at longer distances ISLs can use long-distance dark fiber connections to transfer data. Wavelength-division multiplexing, such as dense wavelength-division multiplexing (DWDM), coarse wavelength-division multiplexing (CWDM), and time-division multiplexing (TDM), can be used to increase the capacity of the links. As Fibre Channel speeds increase, the maximum distance decreases for each switch. The Extended Fabrics feature extends the distance the ISLs can reach over an extended fiber. This extension is accomplished by providing enough buffer credits on each side of the link to compensate for latency introduced by the extended distance. ∙ Simplified management over distance Each device attached to the SAN appears as a local device, which simplifies deployment and administration. ∙ Optimized switch buffering When Extended Fabrics is installed on gateway switches (with E_Port connectivity from one switch to another), the ISLs (E_Ports) are configured with a large pool of buffer credits. The enhanced switch buffers help ensure that data transfer can occur at near-full bandwidth to use the connection over the extended links efficiently. This efficiency ensures the highest possible performance on ISLs. Extended Fabrics device limitations Brocade recommends that you do not use the FC8-64 and FC16-64 port blades for long distance because of their limited buffers. These blades do not support long-wavelength (LWL) fiber optics and only support limited distance. However, you can use the portCfgLongDistance command to reserve frame buffers for the ports intended to be used in long-distance mode through DWDM. There is a limited number of reserved buffers used for long distance for each blade. If some ports are configured in long-distance mode and have buffers reserved for them, insufficient buffers may remain for the other ports. In this case, some of the remaining ports may come up in degraded mode. Brocade Fabric OS Administration Guide, 8.0.1 53-1004111-02 483
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