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Optimizing Your iSCSI Switches

The Brocade FCX line of switches are a great choice for running your iSCSI SAN environment. These switches provide highly desired features such as:

  • Layer 2 & Layer 3 options
  • Built-in stacking with hot-add and hitless fail over abilities
  • 24 & 48 GbE options with 10GbE up link capability
  • Redundant power options.

Brocade FCX iSCSI Best Practice Diagram resized 600iSCSI traffic can be very different from typical Ethernet traffic that you might see coming from workstations or application servers. It requires special care and features to deliver lossless transport to your servers. Features are great but they are nothing without the proper configuration.

So what is the best way to configure a Brocade FCX switch for iSCSI? We have broken the steps out for you:  

1. Enable symmetric flow control. This directive will tell the switch to send pause frames to the connected device when the port (or the entire switch) is oversubscribed. This prevents drops due to overflowing buffers and protects against congestion.
  • Enable globally
    (config)#symmetric-flow-control enable
  • Then for each stack member:
    (config)#symmetric-flow-control enable unit 1
    (config)#symmetric-flow-control enable unit 2

  • Finally, ensure that each port is configured for flow-control negotiation:
    (config)#interface ethernet 1/1/1 to 1/1/24 
    (config-mif-1/1/1-1/1/24)#flow-control neg-on  
2. To optimize the buffers available on the FCX switch, we turn off all limits and priority assignments. All packets get “first-come, first-served” access to buffers in the switch.
  • (config)#buffer-sharing-full

3. Jumbo frames can be controversial and will depend on your SAN provider and your network cards in your servers. If you have end-to-end support of Jumbo frames then we recommend turning this feature on in your FCX switch.
    • (config)#jumbo  
    4. Finally, save the configuration to memory and reload the switch.
    • (config)#write mem 
    • (config)#reload   

    Your Brocade FCX is now ready to optimally handle a dedicated iSCSI environment. If you need to connect other switches (for management or redundant stacks), be sure to disable any spanning tree configuration on the ports that will participate in iSCSI traffic. 

    TBNG Consulting has deployed many dedicated SAN networks utilizing the Brocade FCX line of switches and we couldn’t be happier with the performance and reliability - two qualities that are a MUST HAVE when deploying a SAN. By utilizing our experienced engineers, TBNG can bring your SAN to an enterprise class level you can be proud of.

    Matt Fusaro

    Written by Matt Fusaro


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