Dell PowerEdge FX2/FX2s - Manual (Page 278)

Deciding to Tune Buffers
Dell Networking recommends exercising caution when configuring any non-default buffer settings, as
tuning can significantly affect system performance. The default values work for most cases.
As a guideline, consider tuning buffers if traffic is bursty (and coming from several interfaces). In this case:
• Reduce the dedicated buffer on all queues/interfaces.
• Increase the dynamic buffer on all interfaces.
• Increase the cell pointers on a queue that you are expecting will receive the largest number of
packets.
To define, change, and apply buffers, use the following commands.
• Define a buffer profile for the FP queues.
CONFIGURATION mode
buffer-profile fp fsqueue
• Define a buffer profile for the CSF queues.
CONFIGURATION mode
buffer-profile csf csqueue
• Change the dedicated buffers on a physical interface.
BUFFER PROFILE mode
buffer dedicated
• Change the maximum number of dynamic buffers an interface can request.
BUFFER PROFILE mode
buffer dynamic
• Change the number of packet-pointers per queue.
BUFFER PROFILE mode
buffer packet-pointers
• Apply the buffer profile to a CSF to FP link.
CONFIGURATION mode
buffer csf linecard
Dell Networking OS Behavior: If you attempt to apply a buffer profile to a non-existent port-pipe, the
system displays the following message: %DIFFSERV-2-DSA_BUFF_CARVING_INVALID_PORT_SET:
Invalid FP port-set 2 for linecard 2. Valid range of port-set is <0-1>. However,
the configuration still appears in the running-config.
Configuration changes take effect immediately and appear in the running configuration. Because under
normal conditions all ports do not require the maximum allocation, the configured dynamic allocations
can exceed the actual amount of available memory; this allocation is called oversubscription. If you
choose to oversubscribe the dynamic allocation, a burst of traffic on one interface might prevent other
interfaces from receiving the configured dynamic allocation, which causes packet loss.
You cannot allocate more than the available memory for the dedicated buffers. If the system determines
that the sum of the configured dedicated buffers allocated to the queues is more than the total available
memory, the configuration is rejected, returning a syslog message similar to the following: 00:04:20:
278 Debugging and Diagnostics