HP Cisco MDS 9216 Cisco MDS 9000 Family CLI Configuration Guide, Release 3.x ( - Page 388

Buffer Credit Allocation Chapter 14 Configuring Generation 2 Switches and Modules Send documentation comments to [email protected] Buffer Pools In the architecture of Generation 2 modules, receive buffers shared by a set of ports are called buffer groups. The receive buffer groups are organized into global and local buffer pools. The receive buffers allocated from the global buffer pool to be shared by a port group are called a global buffer pool. Global receive buffer pools include the following buffer groups: • Reserved internal buffers • Allocated BB_credit buffers for each Fibre Channel interface (user configured or assigned by default) • Common unallocated buffer pool for BB_credits, if any, to be used for additional BB_credits as needed • Performance buffers (only used on 12-port 4-Gbps and 4-port 10-Gbps switching modules) Figure 14-1 shows the allocation of BB_credit buffers on linecards (24-port and 48-port line cards). Note In some modules, performance buffers are not supported. Figure 14-1 Receive Buffers for Fibre Channel Ports in a Global Buffer Pool Maximim Receive buffers Total BB_credit buffers 185164 Reserved Internal Buffers (not user configurable) Performance Buffers (Shared Pool) Common unallocated buffer pool for BB_credits Allocated BB_credit buffers 1 23 for each front panel FC ports N Figure 14-2 shows the default BB_credit buffer allocation model for 24-port 4-Gbps switching modules. The minimum BB_credits required to bring up a port is two buffers. Figure 14-2 BB_Credit Buffer Allocation in 24-port 4-Gbps Switching Modules 14-8 Cisco MDS 9000 Family CLI Configuration Guide OL-16184-01, Cisco MDS SAN-OS Release 3.x