Dell Emulex Family of Adapters - Manual (Page 653)

Emulex Drivers for Windows User Manual P010077-01A Rev. A
3. Configuration
NIC Driver Configuration
653
Analyzing Performance Issues
You can use the Windows Performance Monitor (perfmon) to view statistics for each
network device.
To view statistics for each network device:
1. Click Start > Run > perfmon to launch the Windows Performance Monitor.
2. Right-click and select Add Counters to add additional statistics.
Table 3-11 lists a few statistics to use for troubleshooting performance issues. For
network performance, all the counters from the table are useful: Network Interface,
TCPv4, IPv4, and Processor.
Jumbo Packet
The jumbo packet setting in the registry determines the maximum Ethernet packet size.
It includes the Ethernet frame header (typically 14 bytes) but excludes the trailing CRC.
The standard packet size is 1514 bytes plus a 4 byte trailing CRC.
Vendors use many terms that refer to this same quantity, such as packet size, frame
size, or MTU. The MTU is the Ethernet packet payload size. This does not include the
There is a small server struggling to keep up
with larger servers on the network. Disable RSS, enable TCP offload, enable jumbo packets,
and increase the interrupt moderation to allow fewer
interrupts per second.
There is a general purpose server such as
Active Directory server, DHCP server, or a DNS
server. Use TCP offload, and enable RSS.
Table 3-11 Statistics and Fine Tuning
Situation Answer/Solution
Network Interface > Packets Received Errors. If this is incrementing even a small amount, a physical
issue may exist on the network, such as a loose
connection or bad cable, causing CRC errors in Ethernet
packets. Find and eliminate the physical issue.
Network Interface > Packets Received
Discarded. If this is incrementing dramatically, the computer system
may be receiving a lot of unsolicited traffic using
network resources.
IPv4 > Fragmented Datagrams / sec. If this is greater than 0, the computer system is sending
or receiving IP fragments. This is a serious performance
issue. See “Jumbo Packet” on page 653.
TCPv4 > Segments Retransmitted / sec. TCP retransmits indicate that packets are being dropped
by the receiving system (or in a network switch). Ideally,
reduce retransmits to 0.
Processor >% Processor Time. If CPU usage is high, try to enable all available offloads,
such as TCP offload, checksum offloads and use jumbo
packets.
Table 3-10 Windows Server Performance Tuning Situations (Continued)
Situation Answer/Solution