Computation details for VMware metrics

This topic provides computation information for VMware metrics and indicators.

All metrics used in this computation are based on the 95th percentile values of hourly samples of these metrics over the last 30 days. The top 5% spike is not considered.

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 is 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	Penalty	Threshold	Penalty		Computation
MPI Calculation	Penalty	Threshold	Min	Max	Condition	Minimum Penalty multiplier factor
					C/A RATIO >=
Part 1	Consumed/Active Ratio (C/A Ratio)	Configurable Default: 6	5	10	2 x Threshold	2
Part 1	Consumed/Active Ratio (C/A Ratio)	Configurable Default: 6	5	10	1 x Threshold	1
					BALLOONING >=
Part 2	Ballooning	Configurable Default: 1 GB	5	15	3 x Threshold	3
					2 x Threshold	2
					1 x Threshold	1
					OVER-COMMITMENT >=
Part 3	Over-commitment	Configurable Default: 1.2	5	15	Threshold + 0.4	3
					Threshold + 0.2	2
					Threshold	1
					SWAP_RATE >=
Part 4	Swap Rate	Configurable Default: 64 MB/sec	5	30	6 x Threshold	6
					5 x Threshold	5
					4 x Threshold	4
					3 x Threshold	3
					2 x Threshold	2
					1 x Threshold	1
Estimated MPI	If Part 2 = 0: Estimated MPI = Active Memory Utilization + Part 1 + Part 3 + Part 4 Else: Estimated MPI = Active Memory Utilization + Part 2 + Part 3 + Part 4
Actual MPI	Actual MPI = MIN (Consumed Memory Utilization, Estimated MPI)

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

Metrics/Parameters used in MPI calculation	Threshold	Penalty		Computation
Metrics/Parameters used in MPI calculation	Threshold	Min	Max
Memory Swap Out Rate MEM_SWAP_OUT_BYTE_RATE	32 Mbytes/sec	10	50
Swap Rate threshold exceed count	1			count(MEM_SWAP_OUT_BYTE_RATE > threshold (MEM_SWAP_OUT_BYTE_RATE))
				Condition	Penalty for Swap Rate
				Swap Rate threshold_exceed_count > 5 * Minimum swap rate exceed count	5 * MINIMUM_PENALTY
				Swap Rate threshold_exceed_count > 4 * Minimum swap rate exceed count	4 * MINIMUM_PENALTY
				Swap Rate threshold_exceed_count > 3 * Minimum swap rate exceed count	3 * MINIMUM_PENALTY
				Swap Rate threshold_exceed_count > 2 * Minimum swap rate exceed count	2 * MINIMUM_PENALTY
				Swap Rate threshold_exceed_count > 1 * Minimum swap rate exceed count	1 * MINIMUM_PENALTY
Memory Pressure Index = Memory Utilization/2 + Penalty for Swap Rate

Composite Memory computation

Composite Memory is stored as an Indicator and is calculated through the following formula:

Composite Memory Consumption	Min ( Consumed Memory, (Active Memory + ((Consumed Memory – Active Memory) x Memory Pressure Index /100)))
Composite Memory Utilization	Min ( Consumed Memory Util, (Active Memory Util + ((Consumed Memory Util – Active Memory Util) x Memory Pressure Index /100)))

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).

MPI Calculation	Penalty	Threshold	Penalty		Computation
			Min	Max	Condition	Minimum Penalty multiplier factor
					CPU_READY >=
Part 1	Cluster CPU Ready: Cluster CPU Ready = Average of CPU Ready of VMs that exceed CPU Ready threshold	Configurable Default: 10%	5	20	4 x Threshold	4
					3 x Threshold	3
					1 x Threshold	1
					COUNT >=
Part 2	Cluster CPU Ready Exceed Count: Cluster CPU Ready Exceed Count = Number of VMs that exceed threshold	Configurable Default: 10	5	20	4 x Threshold	4
					3 x Threshold	3
					2 x Threshold	2
					1 x Threshold	1
Combined CPI	If CPU_Utilization > CPU_Util_thresh, then: CPU Pressure Index = CPU_Utilization Else: CPU Pressure Index = CPU Utilization + MAX (Part 1, Part 2)

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):

SPI Calculation	Penalty	Threshold	Penalty		Computation
			Min	Max	Condition	Minimum Penalty multiplier factor
					LATENCY >=
Part 1	Cluster I/O Latency: Cluster I/O Latency = Average of I/O Latency of datastores that exceed I/O latency threshold	Configurable Default: 30 msec	5	20	4 x Threshold	4
					3 x Threshold	3
					2 x Threshold	2
					1 x Threshold	1
					COUNT >=
Part 2	Cluster I/O Latency Exceed Count: Cluster IO Latency Exceed Count = Number of Datastores that exceed threshold	Configurable Default: 10	5	20	4 x Threshold	4
					3 x Threshold	3
					2 x Threshold	2
					1 x Threshold	1
Combined SPI	If Storage_Utilization > Storage_Util_thresh, then: Storage Pressure Index = Storage_Utilization Else: Storage Pressure Index = Storage Utilization + MAX (Part 1, Part 2)