6.7

n
On systems with sizable RAM, disable memory trimming by adding the line MemTrimRate=0 to the
virtual machine's VMX file.
n
If the combined disk I/O is higher than a single HBA capacity, use multipathing or multiple links.
n
For ESXi hosts, create virtual disks as preallocated. When you create a virtual disk for a guest
operating system, select Allocate all disk space now. The performance degradation associated with
reassigning additional disk space does not occur, and the disk is less likely to become fragmented.
n
Use the most current hypervisor software.
Solutions for Poor Network Performance
Network performance is dependent on application workload and network configuration. Dropped network
packets indicate a bottleneck in the network. Slow network performance can be a sign of load-balancing
problems.
Problem
Network problems can manifest in many ways:
n
Packets are being dropped.
n
Network latency is high.
n
Data receive rate is low.
Cause
Network problems can have several causes:
n
Virtual machine network resource shares are too few.
n
Network packet size is too large, which results in high network latency. Use the VMware AppSpeed
performance monitoring application or a third-party application to check network latency.
n
Network packet size is too small, which increases the demand for the CPU resources needed for
processing each packet. Host CPU, or possibly virtual machine CPU, resources are not enough to
handle the load.
Solution
n
Determine whether packets are being dropped by using esxtop or the advanced performance charts
to examine the droppedTx and droppedRx network counter values. Verify that VMware Tools is
installed on each virtual machine.
n
Check the number of virtual machines assigned to each physical NIC. If necessary, perform load
balancing by moving virtual machines to different virtual switches 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.
n
If possible, use vmxnet3 NIC drivers, which are available with VMware Tools. They are optimized for
high performance.
vSphere Monitoring and Performance
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