6.7

Transient high-usage values usually do not cause performance degradation. For example, memory usage
can be high when several virtual machines are started at the same time or when a spike occurs in virtual
machine workload. However, a consistently high memory usage value (94% or greater) indicates that the
host is probably lacking the memory required to meet the demand. If the active memory size is the same
as the granted memory size, the demand for memory is greater than the memory resources available. If
the active memory is consistently low, the memory size might be too large.
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. It leads to memory reclamation, which might degrade performance.
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 host has little free memory available, or if you notice a degradation in performance, consider taking
the following actions.
Table 1‑64. 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, it 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.
Memory (MBps)
The Memory (MBps) chart displays the swap in and swap out rates for a host.
This chart is located on the Home view of the Host Performance tab.
vSphere Monitoring and Performance
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