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350-401 Practice Question: Is troubleshooting performance issues on a VMware…
A network engineer is troubleshooting performance issues on a VMware ESXi host running multiple VMs. The host has two physical CPUs, each with 8 cores (16 logical processors with Hyper-Threading enabled). One VM, configured with 8 vCPUs, experiences high CPU ready time. Other VMs on the host are idle. What is the most likely cause of the high CPU ready time?
⚠ Common exam trap
A common misconception is that CPU ready time is always due to overcommitment. However, the trap here is that a VM with vCPUs equal to the number of physical cores per socket can still experience NUMA spanning because the hypervisor may schedule vCPUs across sockets, especially when Hyper-Threading is enabled, causing remote memory access.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The VM's vCPUs span multiple NUMA nodes, causing memory access delays.
The VM has 8 vCPUs, and each physical CPU socket has 8 cores (16 logical processors with Hyper-Threading). While the VM could theoretically be scheduled entirely within one NUMA node (one socket), hypervisors often distribute vCPUs across sockets for load balancing or to avoid resource contention, especially when the VM's vCPU count equals the number of cores per socket. This causes NUMA spanning, leading to remote memory access and higher CPU ready time due to NUMA latency. Hyper-Threading can worsen the issue as vCPUs may be placed on logical processors from different sockets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The VM's vCPUs span multiple NUMA nodes, causing memory access delays.
Why this is correct
Correct because when vCPUs are spread across NUMA nodes, memory access becomes non-local, increasing ready time.
- ✗
Hyper-Threading is disabled on the ESXi host.
Why it's wrong here
Incorrect because Hyper-Threading does not directly cause CPU ready time; it increases available logical CPUs.
- ✗
The host is overcommitted with too many vCPUs.
Why it's wrong here
Incorrect because other VMs are idle, so overcommitment is not the issue.
- ✗
The VM has more vCPUs than physical cores on a single socket.
Why it's wrong here
Incorrect because the VM has 8 vCPUs and each socket has 8 cores, so it fits within one socket.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.