HP Cisco MDS 9020 Cisco MDS 9000 Family Fabric Manager Configuration Guide, Re - Page 443

Chapter 22 Configuring Generation 2 Switches and Modules Configuring Generation 2 Module Interface Shared Resources Send documentation comments to [email protected] Step 5 Click the Apply Changes icon. . Caution Changing port speed and rate mode disrupts traffic on the port. Configuring Oversubscription Ratio Restrictions The 48-port and 24-port 4-Gbps Fibre Channel switching modules support oversubscription on switches with shared rate mode configurations. Table 22-15 describes the bandwidth allocation for oversubscribed interfaces configured in shared mode. Table 22-15 Bandwidth Allocation for Oversubscribed Interfaces Switching Module Type 48 ports 24 ports Configured Speed Auto 4 Gbps Auto (maximum is 2 Gbps) 2 Gbps 1 Gbps Auto 4 Gbps Auto (maximum is 2 Gbps) 2 Gbps 1 Gbps Reserved Bandwidth (Gbps) Maximum Bandwidth Ratios enabled Ratios disabled (Gbps) 0.8 0.09 4 0.4 0.045 2 0.2 0.0225 1 1 0.27 4 0.5 0.135 2 0.25 0.067 1 By default, all 48-port and 24-port 4-Gbps Fibre Channel switching modules have restrictions on oversubscription ratios enabled. As of Cisco SAN-OS Release 3.1(1) and later, you can disable restrictions on oversubscription ratios. All ports in 48-port and 24-port modules can be configured to operate at 4 Gbps in shared mode-even if other ports in the port group are configured in dedicated mode-regardless of available bandwidth. However, when oversubscription ratio restrictions are enabled you may not have all shared ports operating at 4 Gbps. For example, oversubscription ratios are enabled, and you have configured three 4 Gbps dedicated ports in one port group, no other ports in the same port group can be configured to operate at 4 Gbps. For dedicated ports, oversubscription ratio restrictions do not apply to the shared pool in port groups. So if oversubscription ratio restrictions are disabled, and you've configured three 4 Gbps dedicated ports in one port group, then you can configure all other ports in the same port group to operate at a shared rate of 4 Gbps. When disabling restrictions on oversubscription ratios, all ports in shared mode on 48-port and 24-port 4-Gbps Fibre Channel switching modules must be shut down. When applying restrictions on oversubscription ratios, you must take shared ports out of service. OL-16184-01, Cisco MDS SAN-OS Release 3.x Cisco MDS 9000 Family CLI Configuration Guide 22-23