Dell Brocade Adapters - Manual (Page 69)

Brocade Adapters Troubleshooting Guide 45
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DCB network problems
2
Disk I/O requests cause low throughput and high latency on Linux
If a high number of I/O requests is causing low throughput and high latency on Linux systems, refer
to the following descriptions of possible causes and recommended actions to help resolve the
problem.
Possible Cause: The maximum input/output operations per second are too low on Linux hosts.
Action: Refer to “Linux tuning” on page 113 for suggestions to optimize adapter performance in
Linux systems.
Disk I/O requests cause low throughput and high latency on VMware
If a high number of I/O requests is causing low throughput and high latency on VMware systems,
refer to the following descriptions of possible causes and recommended actions to help resolve the
problem.
Possible Cause: The maximum input/output operations per second are too low on VMware hosts.
Action: Refer to “VMware tuning” on page 116 for suggestions to optimize adapter performance in
VMware systems.
DCB network problems
NOTE
This issue applies to CNAs and Fabric Adapter ports configured in CNA mode only.
This section provides information to resolve problems of adapter operation on the Data Center
Bridging (DCB) network. For additional information on troubleshooting problems on mezzanine card
or expansion card adapters, refer to
“Troubleshooting mezzanine card problems” on page 55.
DCB is not enabled
The DCB state does not show “DCB Linkup” when you run the BCU port --query command.
1. Possible Cause: The link between the adapter port and switch is down.
Action: Run the dcb --query command for the port to gain a better understanding of LLDP
attributes, DCB maps, and priority tables configured for the port. Also check the error reason
code for the DCB link failure. The error reason code will tell you why the DCB is not enabled or
active. If the error reason is “Physical Link down,” refer to
“Port link is not active” on page 10
and “Verifying Fibre Channel and DCB links (stand-up adapters)” on page 50.
2. Possible Cause: Adapter did not receive DCB configuration or received invalid DCB
configuration from the FCoE switch.
Action: Run the BCU dcb --query command for the port to gain a better understanding of LLDP
attributes and DCB configuration (such as DCB maps and priority tables) configured for the
port. Also check for the error reason code for the DCB link failure. The reason code will tell you
why the DCB is not enabled or active. Change or fix the DCB configuration at the switch
appropriately based on the displayed error reason code.