VMware 4817V62 - vSphere - PC, Administration Manual

Page: 276 / 364

Table 22-8. Memory Performance Enhancement Advice (Continued)
# Resolution
4 If the memory reservation of the virtual machine is set to a value much higher than its active memory, decrease the
reservation setting so that the VMkernel can reclaim the idle memory for other virtual machines on the host.
5 Migrate one or more virtual machines to a host in a DRS cluster.
6 Add physical memory to the host.
Network Performance
Use the network performance charts to monitor network usage and bandwidth for clusters, hosts, and virtual
machines. Use the guidelines below to identify and correct problems with networking performance.
Network performance is dependent on application workload and network configuration. Dropped network
packets indicate a bottleneck in the network. To determine whether packets are being dropped, use
esxtop
or
the advanced performance charts to examine the
droppedTx
and
droppedRx
network counter values.
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
OTE
In some instances, large packets can result in high network latency. To check 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 different 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.
Table 22-9. 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 ESX/ESXi host communicate with each other, connect them to the same
vSwitch to avoid the cost of 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 different traffic streams, such as network packets generated by virtual
machines, iSCSI protocols, VMotion tasks, and service console activities.
6 Ensure that the physical NIC capacity is large enough to handle the network traffic on that vSwitch. If the capacity
is not enough, consider using a high-bandwidth physical NIC (10Gbps) or 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 buffers where applicable.
8 Verify that the reported speed and duplex settings for the physical NIC match the hardware expectations and that
the hardware is configured to run at its maximum capability. For example, verify that NICs with 1Gbps are not reset
to 100Mbps because they are connected to an older switch.
9 Verify that all NICs are running in full duplex mode. Hardware connectivity issues might result in a NIC resetting
itself to a lower speed or half duplex mode.
10 Use vNICs that are TSO-capable, and verify that TSO-Jumbo Frames are enabled where possible.
vSphere Basic System Administration
276 VMware, Inc.