The Memory (MB) chart displays memory data counters for hosts.

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

Note: Guest physical memory refers to the virtual hardware memory presented to a virtual machine for its guest operating system. Machine memory is the actual physical RAM in the host.

Not all counters are collected at collection level 1.

Table 1. Data Counters
Chart Label Description
Active Sum of the active guest physical memory of all powered on virtual machines on the host, plus memory used by basic VMKernel applications. Active memory is estimated by the VMkernel and is based on the current workload of the host.
  • Counter: active
  • Stats Type: Absolute
  • Unit: Megabytes (MB)
  • Rollup Type: Average (Minimum/Maximum)
  • Collection Level: 2 (4)
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)
Balloon Target Sum of the balloon target memory of all powered on virtual machines on the host.

If the balloon target value is greater than the balloon value, the VMkernel inflates the balloon, causing more virtual machine memory to be reclaimed. If the balloon target value is less than the balloon value, the VMkernel deflates the balloon, which allows the virtual machine to consume additional memory if needed.

Virtual machines initiate memory reallocation. Therefore, it is possible to have a balloon target value of 0 and a balloon value greater than 0.

  • Counter: vmmemctltarget
  • Stats Type: Absolute
  • Unit: Megabytes (MB)
  • Rollup Type: Average (Minimum/Maximum)
  • Collection Level: 2 (4)
Consumed Amount of machine memory used on the host.

Consumed memory includes virtual machine memory, service console memory, and VMkernel memory.

consumed memory = total host memory - free host memory

  • Counter: consumed
  • Stats Type: Absolute
  • Unit: Megabytes (MB)
  • Rollup Type: Average (Minimum/Maximum)
  • Collection Level: 1 (4)
Granted Sum of the guest physical memory granted for all powered on virtual machines. Granted memory is mapped to the host's machine memory.

Granted memory for a host includes the shared memory of each virtual machine on the host.

  • Counter: granted
  • Stats Type: Absolute
  • Unit: Megabytes (MB)
  • Rollup Type: Average (Minimum/Maximum)
  • Collection Level: 2 (4)
Shared Common Amount of machine memory shared by all powered on virtual machines.

Shared common memory consists of the entire pool of memory from which sharing is possible, including the amount of physical RAM required by the guest memory.

memory shared - memory shared common = amount of memory saved on the host from sharing

  • Counter: sharedcommon
  • Stats Type: Absolute
  • Unit: Megabytes (MB)
  • Rollup Type: Average (Minimum/Maximum)
  • Collection Level: 2 (4)
Swap Used Sum of the memory swapped by all powered on virtual machines on the host.
  • Counter: swapused
  • Stats Type: Absolute
  • Unit: Megabytes (MB)
  • Rollup Type: Average (Minimum/Maximum)
  • Collection Level: 2 (4)

Chart Analysis

To ensure best performance, the host memory must be large enough to accommodate the active memory of the virtual machines. The active memory can be smaller than the virtual machine memory size. It 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 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 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, 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.