HP StorageWorks 8/80 HP StorageWorks Fabric OS 6.2 administrator guide (5697-0 - Page 434

Virtual E_Ports and Virtual EX_Ports do not support long distance. The buffer credit recovery feature is enabled for the following flow control modes: Normal, Virtual Channel (VC), and Extended VC modes. An FC_Port that supports BB_Credit recovery, maintains the following BB_Credit recovery values: • BB_SC_N is the log2 of BB_Credit recovery modules • BB_RDY_N counts the number of R_RDY primitives received modulo 2BB_SC_N • BB_FRM_N counts the number of frames received modulo 2BB_SC_N Fabric considerations for buffer credit management Because the number of buffer credits available for use within each port group is limited, configuring buffer credits for extended links may affect the performance of the other ports in the group used for core-to-edge connections. Balance the number of long-distance ISL connections and core-to-edge ISL connections within a switch. Configuring long-distance ISLs between core and edge switches is possible, but is not an HP recommended practice. With the exception of 3xxx series 2Gb and earlier switches, all switch ports provide protection against buffer depletion through buffer limiting. A buffer-limited port reserves a minimum of eight buffer credits, allowing the port to continue to operate rather than being disabled due to a lack of buffers. The eight buffer minimum allows 4 and 8 Gb/s speeds over distances within most data centers. Buffer-limited operations are supported for the L0 and LD extended ISL modes only, and are persistent across reboots, switch disabling and enabling, and port disabling and enabling. Configuring F_Port buffer credits The default configured F_Port buffer credit is fixed at eight buffers. You can use the portCfgFPortBuffers command to configure a given port with the specified number of buffers. To configure a F-Port to use the specified number of buffers: 1. Connect to the switch and log in as admin. 2. Enter the portCfgFPortBuffers command, using the following syntax: portcfgfportbuffers --enable [slot/]port buffers where: slot port buffers For blades, the slot number in which the blade is located. The slot number must be followed by a slash (/) and the port number. This option is not used for fixed-port switches. The port number Specifies the number of buffers to be allocated to the specified port. The specified buffer allocation takes effect when the F_Port comes online. The minimum buffer allocation is the default number of buffers plus 1. The maximum is determined by the remaining buffer allocations in the port's port group. To disable the F_Port buffer configuration and return to the default buffer allocation: portcfgfportbuffers --disable [slot/]port where disable slot port Configures the port to use the default number of buffers Configures a given port with the specified number of buffers Enables or disables buffer credits on the specified port The configured number of buffers for the given port is stored in the configuration database and is persistent across reboots. This feature is not compatible with EX_Port, Port Mirroring, Long-Distance E-Port, L_Port, Fast Write enabled, QoS enabled, and Trunk Area enabled ports. Configuring ports to support long distance To avoid inconsistency in the fabric, make sure that the vc_translation_link_init parameter is enabled on both ends of the link. By default, the VC translation link initialization 430 Administering extended fabrics