Question 389 of 498
VCP-DCV vSphere Performance and Scaling Practice Question
A database VM with 32 vCPUs and 256 GB memory is deployed on a host with two NUMA nodes, each with 8 cores (16 threads with HT). The application performs badly. Analysis shows high remote memory access. What is the MOST LIKELY reason?
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 vNUMA nodes are not aligned with the physical NUMA nodes.
With 32 vCPUs, the VM exceeds the default vNUMA node size of 8 cores per NUMA node, so vSphere exposes multiple vNUMA nodes. However, if the vNUMA topology is not aligned with the physical NUMA nodes (e.g., the VM's vCPUs and memory span physical NUMA boundaries), the guest OS may not optimize memory locality, leading to high remote memory access. Option B correctly identifies this vNUMA misalignment as the most likely cause.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Hyperthreading is enabled causing CPU contention.
Why it's wrong here
Hyperthreading may increase contention but does not directly cause remote memory access.
- ✓
The vNUMA nodes are not aligned with the physical NUMA nodes.
Why this is correct
Misalignment causes the guest to access memory from remote NUMA nodes, increasing latency.
- ✗
The host's NUMA nodes are not balanced in memory capacity.
Why it's wrong here
While unbalanced memory capacity could contribute, the primary issue is vCPU/vMEM alignment with NUMA topology.
- ✗
The VM has too much memory allocated.
Why it's wrong here
More memory does not inherently cause remote access; alignment is key.
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Same concept, more angles
2 more ways this is tested on VCP-DCV
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A large VM with 24 vCPUs is deployed on a dual-socket host with two NUMA nodes each having 12 cores. Which step is a BEST PRACTICE to ensure optimal performance for this VM?
medium- A.Disable hyperthreading on the host to reduce contention.
- B.Assign all vCPUs to a single NUMA node using CPU affinity.
- ✓ C.Leave vNUMA enabled and ensure the VM has enough memory to span two nodes.
- D.Set the VM memory reservation to zero to allow transparent page sharing.
Why C: Setting vNUMA controls exposes the NUMA topology to the guest OS, allowing it to optimize memory locality. By default, vNUMA is enabled for VMs with more than 8 vCPUs. Placing the VM on a single NUMA node would limit resources. Disabling hyperthreading is unnecessary. Setting CPU affinity reduces flexibility.
Variation 2. Which two factors most directly influence vSphere NUMA scheduling decisions for a VM? (Choose two.)
easy- ✓ A.Host NUMA node topology
- B.VM memory reservation
- ✓ C.Number of vCPUs
- D.VM storage policy
- E.Virtual machine version
Why A: The correct options are A and C. vSphere NUMA scheduling uses the number of vCPUs and the host NUMA node topology to place the VM on a single node. Memory reservation and VM version are secondary. Storage policy is not relevant.
Last reviewed: Jun 24, 2026
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