Dell Brocade G620 Brocade 8.0.1 Fabric OS Administratiors Guide - Page 121
Lossless core, ICL limitations, Configuring Lossless Dynamic Load Sharing
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Routing Traffic 2. Applies the results of the rebalance calculations. 3. If IOD is enabled, waits for sufficient time for frames already received to be transmitted. This is needed to maintain IOD. 4. Resumes traffic. The following table shows the effect of frames when you have a specific routing policy turned on with IOD. TABLE 11 Combinations of routing policy and IOD with Lossless DLS enabled Policy IOD Rebalance result with Lossless DLS enabled Port-based Disabled No frame loss, but out-of-order frames may occur. Port-based Exchange-based Exchange-based Enabled Disabled Enabled No frame loss and no out-of-order frames. Topology restrictions apply. Intended for FICON environment. No frame loss, but out-of-order frames may occur. No frame loss and no out-of-order frames. Topology restrictions apply. Intended for FICON environment. Device-based Disabled No frame loss, but out-of-order frames may occur. Device-based Enabled No frame loss and no out-of-order frames. Topology restrictions apply. Intended for FICON environment. NOTE Not only the link cost has influence on DLS, but the order of ports that become online and the speeds of each E_Port or F_Port also have an impact on how the switch calculates or chooses the path using DLS. Lossless core Lossless core works with the default configuration of the Brocade DCX 8510 Backbones and X6 Directors to prevent frame loss during a core blade removal and insertion. This feature is on by default and cannot be disabled. Lossless core has the following limitations: ∙ Only supported with IOD disabled, which means Lossless core cannot guarantee in-order delivery of exchanges ∙ ICL limitations ∙ Traffic flow limitations ICL limitations If ICL ports are connected during a core blade removal, it is equivalent to removing external E_Ports which may cause I/O disruption on the ICL ports that have been removed. If ICL ports are connected during a core blade insertion, it is equivalent to adding external E_Ports which may cause I/O disruption because of reroutes. Lossless DLS, if enabled, takes effect to prevent I/O disruption. NOTE Before you replace the core blades, enable lossless so that the portDecom can decommission the E_Ports losslessly and bring up the E_Ports back losslessly. Configuring Lossless Dynamic Load Sharing You can configure Lossless DLS on either a switch- or chassis-wide basis by using the dlsSet command to specify that no frames are dropped while rebalancing or rerouting traffic. NOTE For more information regarding DLS or E_Port balancing, refer to the dlsset command in the Fabric OS Command Reference. Brocade Fabric OS Administration Guide, 8.0.1 53-1004111-02 121
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