Cisco Systems DSC9148D8G48PK9 manual Performance Buffers, Buffer Pools

Chapter 4 Configuring Interface Buffers

Information About Interface Buffers

•For Generation 2, Generation 3, and Generation 4 switching modules, see the “Buffer Pools” section on page 4-2.

Note In the Cisco MDS 9100 Series switches, the groups of ports on the left outlined in white are in dedicated rate mode. The other ports are host-optimized. Each group of 4 host-optimized ports have the same features as for the 32-port switching module.

Note Because Generation 1 modules do not support as many buffer-to-buffer credits as Generation 4 modules supports, you cannot configure an ISL on E or TE ports between a Generation 1 module such as the

16-port 1-, 2-Gbps Fibre Channel Switching Module (DS-X9016) and a Generation 4 module such as the 48 port 8-Gbps Advanced Fibre Channel module (DS-X9248-256K9) or the 32-port 8-Gbps Advanced Fibre Channel module (DS-X9232-256K9).

Performance Buffers

Regardless of the configured receive BB_credit value, additional buffers, called performance buffers, improve switch port performance. Instead of relying on the built-in switch algorithm, you can manually configure the performance buffer value for specific applications (for example, forwarding frames over FCIP interfaces).

Note Performance buffers are not supported on the Cisco MDS 9148 Fabric Switch, Cisco MDS 9124 Fabric Switch, the Cisco Fabric Switch for HP c-Class BladeSystem, and the Cisco Fabric Switch for IBM BladeCenter.

For each physical Fibre Channel interface in any switch in the Cisco MDS 9000 Family, you can specify the amount of performance buffers allocated in addition to the configured receive BB_credit value.

The default performance buffer value is 0. If you set the performance buffer value to 0, the built-in algorithm is used. If you do not specify the performance buffer value, 0 is automatically used.

The default performance buffer value is 0. If you use the default option, the built-in algorithm is used. If you do not specify this command, the default option is automatically used.

Buffer Pools

In the architecture of Generation 2, Generation 3, and Generation 4 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 receive 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)

	Cisco MDS 9000 Family NX-OS Interfaces Configuration Guide
4-2	OL-29284-01, Release 6.x