HP Cisco Nexus 5000 Cisco MDS 9000 Family CLI Configuration Guide - Release 4. - Page 392

Buffer Credit Allocation Chapter 15 Configuring Generation 2 and Generation 3 Switching Modules Send documentation comments to [email protected] Table 15-6 Dedicated Rate Mode Bandwidth Reservation for Generation 3 Fibre Channel Modules (continued) Part Number DS-X9248-48K9 Product Name/ Description 4/44-port 8-Gbps Host-Optimized Fibre Channel switching module Dedicated Maximum Bandwidth Allowed Ports per Port that can come up Ports in Shared Mode 8 Gbps 4 Gbps 2 Gbps 1 Gbps 4 Ports 12 Ports 24 Ports 48 Ports All the remaining ports are 4 Gbps shared (8 Gbps of bandwidth can be provided only to one port per port group in Dedicated or Shared rate mode). Dynamic Bandwidth Management On port switching modules where bandwidth is shared, the bandwidth available to each port within a port group can be configured based on the port rate mode and speed configurations. Within a port group, some ports can be configured in dedicated rate mode while others operate in shared mode. Ports configured in dedicated rate mode are allocated the required bandwidth to sustain a line rate of traffic at the maximum configured operating speed, and ports configured in shared mode share the available remaining bandwidth within the port group. Bandwidth allocation among the shared mode ports is based on the operational speed of the ports. For example, if four ports operating at speeds 1 Gbps, 1 Gbps, 2 Gbps, and 4 Gbps share bandwidth of 8 Gbps, the ratio of allocation would be 1:1:2:4. Out-of-Service Interfaces On supported modules and fabric switches, you might need to allocate all the shared resources for one or more interfaces to another interface in the port group or module. You can take interfaces out of service to release shared resources that are needed for dedicated bandwidth. When an interface is taken out of service, all shared resources are released and made available to the other interface in the port group or module. These shared resources include bandwidth, rate mode, BB_credits, and extended BB_credits. All shared resource configurations are returned to their default values when the interface is brought back into service. Corresponding resources must be made available in order for the port to be successfully returned to service. Caution If you need to bring an interface back into service, you might disrupt traffic if you need to release shared resources from other interfaces in the same port group. Buffer Credit Allocation This section describes how buffer credits are allocated to switches and modules, and includes the following topics: • Buffer Pools, page 15-9 • BB_Credit Buffers for Switching Modules, page 15-11 • BB_Credit Buffers for Fabric Switches, page 15-21 15-8 Cisco MDS 9000 Family CLI Configuration Guide OL-18084-01, Cisco MDS NX-OS Release 4.x