Computation details for VMware metrics
VMware - Memory Pressure Index
Memory Utilization for clusters, hosts, and VMs reported by VMware, provide only one aspect of memory contention. It does not take into account many other factors that affect memory demand. In addition, memory utilization for clusters, hosts and VMs are based on Consumed Memory which gives an inflated picture of memory usage. In addition to Consumed Memory, VMware reports Active Memory that provides a deflated picture of memory usage.
Memory Pressure Index (MPI) takes into account consumed memory, active memory, and other metrics like ballooning and swapping and provides a realistic picture of the memory pressure in VMware Clusters, Hosts, and VMs (Windows VMs only). MPI is used to compute Composite Memory Utilization and Composite Memory Consumption. Composite Memory Utilization and Composite Memory Consumption are alternate values for Memory Utilization and Consumed Memory computed using MPI.
The following tables describe the computation and other important details for Memory Pressure Index (MPI):
MPI calculation for Clusters and Hosts
The following points about MPI for clusters and hosts should be noted:
- MPI Value: MPI will have a value in the range of 0 – 100. The higher the number, the higher the pressure.
- Minimum value: Minimum value of memory pressure = Active Memory Utilization
- Penalty points: There are penalty points for Consumed/Active Ratio, Ballooning, Over-commitment, and Swapping scenarios, which are described in the following table.
MPI Calculation for VMs (Windows only)
The following points about MPI for VMs should be noted:
- MPI value: MPI will have a value in the range of 0 – 100. The higher the number, the higher the pressure.
- Minimum value: Minimum value of memory pressure = Memory Utilization/2.
- Penalty points: The penalty is calculated based on the value of the memory swap rate.
Metrics/Parameters Used in MPI Calculation
Composite Memory computation
Composite Memory is stored as an Indicator and is calculated through the following formula:
VMware - CPU Pressure Index
CPU Utilization of the cluster or host, reported by VMware, provides the overall CPU consumption of the cluster or host but will not reflect any problems with capacity or performance of individual VMs.
The CPU Pressure Index (CPI) uses the CPU Ready of the VMs in addition to the CPU Utilization to present a better picture of CPU contention in the cluster or host. It is an index between 0 and 100. The higher the value, the higher the pressure. This metric is calculated for VMware hosts and clusters.
The following points about CPI should be noted:
- CPI Value: CPU Pressure has a value in the range of 0 – 100. The higher the number, the higher the pressure.
- Minimum value: Minimum value of CPU pressure = CPU Utilization. If the CPI value is higher than the CPU Utilization, it indicates that some of the VMs are not getting enough CPUs. Review the CPU Starved VMs tab on the Watchlist page in the vSphere Virtual Machines view to check if the VMs running in the cluster have high CPU time. Accordingly, you need to allocate more resources to such VMs.
- Penalty Points: There are Penalty Points for Cluster CPU Ready Time and Cluster CPU Ready Exceed Count scenarios, which are described in the following table with computation and other details for CPU Pressure Index (CPI).
VMware - Storage Pressure Index
An index between 0 and 100 is calculated using Storage utilization and Datastore I/O latency. The higher the value, the higher the pressure. This metric is calculated for vSphere hosts and clusters.
The following points about SPI should be noted:
- SPI Value: The Storage Pressure Index will be between 0 and 100. The higher the number, the higher the pressure.
- Minimum value: Minimum value of Storage pressure = Storage Utilization
- Penalty Points: There are Penalty Points for High I/O Latency Time scenarios, which are described in the following table with computation and other important details for Storage Pressure Index (SPI):