Memory (Balloon)

The Memory (Balloon) chart displays balloon memory on a host.

This chart is located in the Home view of the Host Performance tab.

Table 57. Data Counters

Chart Label	Description
Balloon	Sum of the guest physical memory reclaimed by the balloon driver for all powered on virtual machines on the host. ■ Counter: vmmemctl ■ Stats Type: Absolute ■ Unit: MegaBytes (MB) ■ Rollup Type: Average (Minimum/Maximum) ■ Collection Level: 1 (4)

Charts Analysis

To ensure best performance, the host memory must be large enough to accommodate the active memory of the virtual machines. Note that the active memory can be smaller than the virtual machine memory size. This allows you to over-provision memory, but still ensures that the virtual machine active memory is smaller than the host memory.

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 there is a spike 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, 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. This leads to memory reclamation which may 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 degredation in performance, consider taking the actions listed in Table 58.

Table 58. 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.