Many enterprises are looking to implement or improve business continuity with SAN extension over distance. There are multiple solutions for SAN extension available, each with different strengths. Native Fibre Channel can be extended for hundreds of kilometers but dedicated fibre can be expensive and not easy to deploy. IP-based distance extension can be a cost-effective alternative for many business continuity and disaster recovery solutions. However, the latency and packet loss common on IP networks must be tolerated in order to achieve acceptable disaster recovery performance.

How does Brocade compare?

With the introduction of the Brocade 7500 and the Brocade FR4-18i director blade delivers industry-leading FCIP distance extension. Brocade gives customers the most virtual tunnels per gigabit ethernet port, as well as the highest throughput even over networks with appreciable latency and packet loss. Remote and local sites are protected from fabric reconfigurations by simple-to-administer zoning in conjunction with Brocade's Fibre Channel Routing technology. (Brocade Virtual Fabrics are available on every director and switch running FOS 5.2 whether or not the FR4-18i is present.)

Connectivity between fabrics is enabled using well-understood zoning, minimizing exposure to fabric rebuilds and other disruptions brought on by unpredictable IP networks. Redundancy and load balancing is assured by exchange-based load balancing. In addition to the two hardware optimized Gigabit Ethernet ports, the Brocade 7500 provides 16 full-speed 4 Gbit/sec FC ports, ideal for providing storage and server connectivity at remote sites. The Brocade FR4-18i delivers 8 virtual tunnels per Gigabit Ethernet port, meaning 16 disaster recovery sites with redundant FCIP links can backup to a single director blade. For those companies that want to physically isolate their FCIP solution or not deploy a director at a remote site, the Brocade 7500 has the same performance characteristics as the Brocade FR4-18i but in a single rack standalone unit ideal for a remote data center.

If the SAN administrator has dark fibre between sites, they can use a Brocade FR4-18i blade or 7500 to deliver Fibre Channel Write Acceleration. (Note that this is distinct from FCIP write acceleration, something Brocade has provided for several years.) FC Write Acceleration is easy enabled by adding the host and target into zones with the prefix "FCCAC_" on fabrics on both ends of the dark fibre link. Not only is FC Write Acceleration easy to set up, but it is easy to maintain and easy to troubleshoot.

Regardless of the form factor, each MDS gigabit Ethernet port supports only three virtual tunnels*, significantly limiting the disaster recovery fan-out ratio and greatly increasing the capital cost for the disaster recovery site's FCIP ports. Cisco's 3-tunnel limit means that in the same 16 disaster recovery fan-in scenario, customers must deploy double the number of MPS 18/4 modules than Brocade. While Cisco sells an 8 port IP linecard , these cards are not capable of line-rate performance - a recent customer tape backup test showed that while a single Brocade FCIP port moved 120 MB/sec, four Cisco IP ports only ran at a total of 140 MB/sec, even with VRRP/Etherchannel.) Customers may need to buy expensive enterprise licenses for every switch in every remote site that fans into a disaster recovery center and maintain zoning on top of Inter-VSAN Routing on top of VSANs, introducing unnecessary complexity, expense and risk into an already intricate disaster recovery solution.

Cisco does not support Fibre Channel Fast Write on the MPS 18/4 or the previous generation MPS 14/2. Instead, users are required to install an SSM blade. Not only is the FC Fast Write configuration non-trivial, the first-generation 2Gbit/sec SSM cuts the number of usable ports in a 9513 in half to just 252 per chassis.

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