VCP-DCV vSphere Performance and Scaling Practice Question
A financial services company has a vSphere cluster with four hosts, each equipped with 2 CPU sockets (10 cores each, hyperthreading enabled) and 512 GB RAM. The cluster runs a mix of production and test VMs. Recently, a critical trading application VM (8 vCPUs, 64 GB RAM) was moved by DRS to a host that also runs an analytics workload (4 vCPUs, 32 GB RAM). After the move, the trading application's performance degraded significantly. The administrator checks vCenter performance charts and sees that the trading VM's CPU ready time has increased from 2% to 20% since the migration, while the host's overall CPU utilization is only 50%. The analytics VM shows normal performance. What is the most likely cause of the performance degradation?
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 trading VM is spanning multiple NUMA nodes on the destination host.
The trading VM has 8 vCPUs, and the destination host has two NUMA nodes (one per socket). With hyperthreading, each node has 10 cores × 2 threads = 20 logical CPUs. An 8-vCPU VM may be scheduled across both NUMA nodes, causing remote memory access latency when a vCPU accesses memory that is local to the other node. This latency can manifest as increased CPU ready time (stalls) and degraded performance. The analytics VM with 4 vCPUs likely fits within one node, so its performance remains normal. Option B correctly identifies NUMA spanning. Option A is less plausible because NUMA interleaving is a BIOS setting that would affect all VMs, not just after migration. Option C is unlikely because CPU affinity is not automatically changed by DRS. Option D is incorrect because memory overcommitment is not present (host has 512GB, VMs use only 96GB).
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 host has NUMA node interleaving enabled in BIOS.
Why it's wrong here
NUMA interleaving could cause issues, but it's a BIOS setting, not something that changes on migration.
- ✓
The trading VM is spanning multiple NUMA nodes on the destination host.
Why this is correct
Spanning NUMA nodes can cause remote memory access, increasing memory latency and CPU ready time.
- ✗
The trading VM's CPU affinity is incorrectly set after migration.
Why it's wrong here
CPU affinity is not automatically changed by DRS; it would be a preexisting issue.
- ✗
The host has insufficient memory to run both VMs, causing memory overcommitment.
Why it's wrong here
The host has 512 GB RAM, and only 96 GB is allocated, so memory is not overcommitted.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This VCP-DCV practice question is part of Courseiva's free VMware 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 VCP-DCV exam.