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.

Table 1. Data Counters
Chart Label Description
swapinRate Average rate at which memory is swapped in from the host swap file.
  • Counter: swapinRate
  • Stats Type: Rate
  • Unit: MegaBytes per second (MBps)
  • Rollup Type: Average (Minimum/Maximum)
  • Collection Level: 1 (4)
swapoutRate Average rate at which memory is swapped out to the host swap file.
  • Counter: swapoutRate
  • Stats Type: Rate
  • Unit: MegaBytes per second (MBps)
  • Rollup Type: Average (Minimum/Maximum)
  • Collection Level: 1 (4)

Chart Analysis

Host memory must be large enough to accommodate virtual machine workload. 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 the host does not have the memory resources required to meet the demand. If the memory balloon and swap values are not high, performance is probably not affected. 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 requires more memory resources.

If the host is not lacking memory resources, 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 is lacking memory resources or you notice a degredation in performance, consider taking the following actions.

Table 2. 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 a 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.