Installation guide

If the host has enough free memory, check the resource shares, reservation, and limit settings of the virtual
machines and resource pools on the host. Verify that the host settings are adequate and not lower than those
set for the virtual machines.
If the memory usage value is high, and the host has high ballooning or swapping, check the amount of free
physical memory on the host. A free memory value of 6% or less indicates that the host cannot handle the
demand for memory. This leads to memory reclamation which may degrade performance.
If memory usage is high or you notice degredation in performance, consider taking the actions listed below.
Table 22-8. Memory Performance Enhancement Advice
# Resolution
1 Verify that VMware Tools is installed on each virtual machine. The balloon driver is installed with VMware Tools
and is critical to performance.
2 Verify that the balloon driver is enabled. The VMkernel regularly reclaims unused virtual machine memory by
ballooning and swapping. Generally, this does not impact virtual machine performance.
3 Reduce the memory space on the virtual machine, and correct the cache size if it is too large. This frees up memory
for other virtual machines.
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.
NOTE 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.
vSphere Basic System Administration
282 VMware, Inc.