Overallocated VM recommendation
The Overallocated VM recommendation identifies virtual machines (VMs) with underutilized resources (CPU, memory, or storage).
The recommended action specifies the resource identifier of the overallocated VM (source VM) and suggests an ideal size for the VM (target VM) to avoid wastage and reduce costs.
For a source VM that is in the public cloud, the recommended instance type for the target VM belongs to the same family as that of the source. For example, if the source VM is of type General Purpose - M4, then the recommended target instance can belong to M3 or M5, depending on the computed ideal size.
If TrueSight Cloud Cost Control is installed, the recommended action also includes the estimated cost savings (in $) per month.
Overallocated VM detection
A VM is detected to be overallocated if the spare capacity of its resources (CPU, memory, storage) exceeds the corresponding threshold (specified in the Optimizer rule).
The spare capacity of a resource is the difference between its actual configured value and its estimated future usage value. You can reconfigure or modify the spare capacity thresholds in the Optimizer rule.
The following table lists the default values of the configuration parameters that are used to generate the recommendation and links to topics that explain how you can reconfigure or modify them.
vSphere VM Active Memory increase factor = 50 %
|Parameters and thresholds in the Optimizer rule (Conditions section)|
Ideal size computation of the target VM
The ideal size of the target VM is suggested by considering the estimated future usage and the estimated past usage of the resources.
The estimated past usage value of each resource is computed based on the selected Optimization behavior (Aggressive, Balanced, Conservative) and stored in the corresponding .
For VMs that are provisioned in the public cloud: The resizing recommendation for the CPU resource also considers CPU benchmark. The estimated CPU benchmark value of the source VM is compared with that of the probable target VMs and the VM with the best match is recommended.
If the CPU benchmark value for the source VM is unavailable, then the resizing recommendation is generated without considering benchmarks.
SPECint_rate2006 is used as the reference benchmark to compare the hardware of the source and target VMs. The CPU benchmark consideration is to ensure that the suggested target VM performs at the same computing power as that of the source VM, even if the hardware is different.
Past usage estimation
The following table explains how the past usage is computed per optimization behavior:
Resource utilization in the server is computed by considering the average value of hourly samples. Spikes in the resource utilization within the hour are not considered. Then, 95th percentile of the hourly value over the last 30 days is computed for each resource to generate the configuration of the target virtual machine or instance type.
Resource utilization in the server is computed by considering the 90th percentile value of hourly samples. Only 10% of spikes in the utilization within the hour are not considered. Then, 95th percentile of the hourly value over the last 30 days is computed for each resource to generate the configuration of the target virtual machine or instance type.
Resource utilization in the server is computed by considering the 99th percentile value of hourly samples. Only 1% of spikes in the utilization within the hour are not considered. Then, 95th percentile of the hourly value over the last 30 days is computed for each resource to generate the configuration of the target virtual machine or instance type.
If you select the Conservative or Balanced optimization behavior for a server that is not instrumented, the results are based on the Aggressive behavior.
BMC recommends the Conservative behavior for servers that are running business-critical applications.
Other recommendation details
The Overallocated VM recommendation window displays an Accuracy icon that indicates the accuracy or reliability of the resizing suggestion given in the recommended actions. The accuracy level shown in the icon is based on the selected Optimization behavior. For more information about the accuracy levels, see Accuracy levels of resizing recommendations for overallocated VMs.
Where to go from here
To view the overallocated VM recommendations, see the Recommendations page of the capacity view of the supported cloud provider and technology:
- Recommendations page in the AWS EC2 Instances view
- Recommendations page in the Azure Virtual Machines view
- Recommendations page in the Hyper-V Overview view
- Recommendations page in the vSphere Virtual Machines view