6.5.1

If packets are being dropped, adjust the virtual machine shares. If packets are not being dropped, check the
size of the network packets and the data receive and transfer rates. In general, the larger the network
packets, the faster the network speed. When the packet size is large, fewer packets are transferred, which
reduces the amount of CPU required to process the data. When network packets are small, more packets are
transferred but the network speed is slower because more CPU is required to process the data.
N In some instances, large packets might result in a high network latency. To check the network latency,
use the VMware AppSpeed performance monitoring application or a third-party application.
If packets are not being dropped and the data receive rate is slow, the host is probably lacking the CPU
resources required to handle the load. Check the number of virtual machines assigned to each physical NIC.
If necessary, perform load balancing by moving virtual machines to dierent vSwitches or by adding more
NICs to the host. You can also move virtual machines to another host or increase the host CPU or virtual
machine CPU.
If you experience network-related performance problems, also consider taking the following actions.
Table 1‑118. Networking Performance Enhancement Advice
# Resolution
1 Verify that VMware Tools is installed on each virtual machine.
2 If possible, use vmxnet3 NIC drivers, which are available with VMware Tools. They are optimized for high
performance.
3 If virtual machines running on the same host communicate with each other, connect them to the same vSwitch to
avoid transferring packets over the physical network.
4 Assign each physical NIC to a port group and a vSwitch.
5 Use separate physical NICs to handle the dierent trac streams, such as network packets generated by virtual
machines, iSCSI protocols, vMotion tasks.
6 Ensure that the physical NIC capacity is large enough to handle the network trac on that vSwitch. If the capacity
is not enough, consider using a high-bandwidth physical NIC (10 Gbps). Alternatively, consider moving some
virtual machines to a vSwitch with a lighter load or to a new vSwitch.
7 If packets are being dropped at the vSwitch port, increase the virtual network driver ring buers where applicable.
8 Verify that the reported speed and duplex seings for the physical NIC match the hardware expectations and that
the hardware is congured to run at its maximum capability. For example, verify that NICs with 1 Gbps are not
reset to 100 Mbps because they are connected to an older switch.
9 Verify that all NICs are running in full duplex mode. Hardware connectivity problems might result in a NIC
reseing itself to a lower speed or half duplex mode.
10 Use vNICs that are TCP Segmentation Ooad (TSO)-capable, and verify that TSO-Jumbo Frames are enabled
where possible.
Network Packets (Number)
The Network Packets monitors network bandwidth for virtual machines.
This chart is located in the Home view of the Virtual Machine Performance tab. It appears only at collection
levels 3 and 4.
vSphere Monitoring and Performance
82 VMware, Inc.