Fabric OS Administrator's Guide v7.0.0 (53-1002148-02, June 2011)

Fabric OS Administrator’s Guide 299
53-1002148-02
Chapter
13
Bottleneck Detection
In this chapter
•Bottleneck detection overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
•Supported configurations for bottleneck detection . . . . . . . . . . . . . . . . . . 302
•Advanced bottleneck detection settings . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
•Enabling bottleneck detection on a switch . . . . . . . . . . . . . . . . . . . . . . . . . 304
•Excluding a port from bottleneck detection. . . . . . . . . . . . . . . . . . . . . . . . . 305
•Displaying bottleneck detection configuration details . . . . . . . . . . . . . . . . 305
•Changing bottleneck parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
•Displaying bottleneck statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
•Disabling bottleneck detection on a switch. . . . . . . . . . . . . . . . . . . . . . . . . 310
Bottleneck detection overview
A bottleneck is a port in the fabric where frames cannot get through as fast as they should. In other
words, a bottleneck is a port where the offered load is greater than the achieved egress
throughput. Bottlenecks can cause undesirable degradation in throughput on various links. When a
bottleneck occurs at one place, other points in the fabric can experience bottlenecks as the traffic
backs up.
The bottleneck detection feature enables you to do the following:
• Prevent degradation of throughput in the fabric.
The bottleneck detection feature alerts you to the existence and locations of devices that are
causing latency. If you receive alerts for one or more F_Ports, use the CLI to check whether
these F_Ports have a history of bottlenecks.
• Reduce the time it takes to troubleshoot network problems.
If you notice one or more applications slowing down, you can determine whether any latency
devices are attached to the fabric and where. You can use the CLI to display a history of
bottleneck conditions on a port. If the CLI shows above-threshold bottleneck severity, you can
narrow the problem down to device latency rather than problems in the fabric.
You can use the bottleneck detection feature with other Adaptive Networking features to optimize
the performance of your fabric. For example, you can do the following:
• If the bottleneck detection feature detects a latency bottleneck, you can use TI zones or QoS
SID/DID traffic prioritization to isolate latency device traffic from high priority application
traffic.
• If the bottleneck detection feature detects ISL congestion, you can use ingress rate limiting to
slow down low priority application traffic, if it is contributing to the congestion.