The Nutanix ECA course provides guidance on performance monitoring and troubleshooting for VMs, including metrics to analyze when determining whether additional vCPUs are needed. The scenario involves a VM experiencing performance issues, with the cluster performing well overall, suggesting the issue is VM-specific.
Extract from Nutanix Enterprise Cloud Administration (ECA) Course Documents:
Module: Performance Monitoring, Section: VM Performance Metrics"To determine if a VM requires additional vCPUs, analyze VM CPU Usage and VM CPU Ready Time. High CPU Usage indicates the VM is under heavy load, while high CPU Ready Time suggests the VM is waiting for CPU resources, both justifying additional vCPUs."
Module: Troubleshooting, Section: VM Performance Issues"When a VM experiences performance issues, VM CPU Usage and VM CPU Ready Time are critical metrics. CPU Usage shows demand, while CPU Ready Time indicates contention or scheduling delays, helping determine if more vCPUs are warranted."
Explanation of Options:
A. VM CPU UsageThis is correct. VM CPU Usage measures the percentage of CPU resources the VM is consuming. High CPU Usage (e.g., consistently above 80–90%) indicates that the VM is under heavy load and may benefit from additional vCPUs to handle the workload. The ECA course emphasizes:"VM CPU Usage is the primary metric to assess whether a VM’s CPU allocation is sufficient for its workload."
B. VM CPU Ready TimeThis is correct. VM CPU Ready Time measures the time a VM is ready to run but waiting for CPU resources from the hypervisor due to contention or oversubscription. High CPU Ready Time (e.g., above 5–10%) suggests that the VM is not getting enough CPU cycles, and adding vCPUs could alleviate the issue. The ECA course notes:"High VM CPU Ready Time indicates CPU contention, often resolved by adding vCPUs or optimizing resource allocation."
C. Host Memory Swap Out RateThis is incorrect. Host Memory Swap Out Rate indicates memory pressure on the host, causing memory pages to be swapped to disk. While this can affect VM performance, it is unrelated to CPU performance and does not justify adding vCPUs. The ECA course states:"Host Memory Swap Out Rate is relevant for memory-related issues, not CPU allocation decisions."
D. Host CPU UsageThis is incorrect. Host CPU Usage measures the overall CPU utilization of the host, not the specific VM. Since the cluster is performing well overall, high Host CPU Usage is unlikely, and it does not directly indicate whether the VM needs more vCPUs. The ECA course clarifies:"Host CPU Usage is a cluster-wide metric and less relevant for diagnosing VM-specific CPU performance issues."
Additional Context from ECA:
Performance Monitoring Tools: In Prism Element or Prism Central, VM CPU Usage and CPU Ready Time can be monitored underVM > Monitoror through dashboards. These metrics provide insight into the VM’s CPU demand and contention.
Adding vCPUs: The ECA course advises caution when adding vCPUs, as over-allocation can increase CPU Ready Time due to scheduling overhead. However, if both CPU Usage and Ready Time are high, adding vCPUs is justified.
Supporting Reference from Web Results:
The Nutanix Bible (https://www.nutanix.com/go/the-nutanix-bible) supports: "For VM performance issues, analyze VM CPU Usage and CPU Ready Time to determine if additional vCPUs are needed, as these metrics directly indicate CPU demand and contention."
