Brocade Fabric OS Administrator's Guide Supporting Fabric OS v6.3.0 (53-1001336-02, November 2009)

Fabric OS Administrator’s Guide 437

53-1001336-02

Bottleneck detection

• Bottleneck detection is supported whether Virtual Fabrics is enabled or disabled. See “Virtual

Fabrics considerations for bottleneck detection” on page 438 for additional information on

using bottleneck detection if Virtual Fabrics is enabled.

How bottlenecks are reported

Bottlenecks are reported through RASlog alerts. You can set alert thresholds for the severity and

duration of the bottleneck.

You can also use a CLI command to display a history of bottleneck conditions on a port. A history is

maintained for a maximum of three hours for each port.

Which ports should have bottleneck detection

Bottleneck detection is disabled by default, and must be explicitly enabled for each port that is to

be monitored.

Because most latency bottlenecks occur on ports connected to targets, it is a good practice to

enable bottleneck detection on all supported F_Ports and FL_Ports that are connected to targets.

After you enable bottleneck detection on a port, you can leave it enabled and do not need to

disable it.

Limitations of bottleneck detection

The bottleneck detection feature does not detect link overutilization. Using this feature is not

recommended for link utilizations above 85%.

The bottleneck detection feature detects latency bottlenecks at the fabric edge, at an F_Port or

FL_Port. It does not detect ISL bottlenecks.

The bottleneck detection feature detects latency bottlenecks only at the point of egress, not

ingress.

High availability considerations for bottleneck detection

The bottleneck detection configuration (ports where enabled and thresholds) is maintained across

a failover or reboot; however, bottleneck statistics collected are lost.

Upgrade and downgrade considerations for bottleneck detection

The configuration files for bottleneck detection are persistent across firmware upgrades and

downgrades.

If you downgrade to a firmware version earlier than Fabric OS v6.3.0, bottleneck detection is no

longer supported. If you later upgrade to Fabric OS 6.3.0 or later, the switch attempts to enable the

bottleneck detection settings that were enabled before the downgrade.