NFS Port Binding for Performance
An administrator notices that a virtual machine on an NFS datastore is experiencing intermittent performance degradation. The ESXi hosts are connected to the NFS server via a 10 GbE network. The administrator uses esxtop and sees high average latency on the storage device, but the NFS server reports low latency. What is the most likely cause?
⚠ Common exam trap
VCP-DCV often tests the ability to differentiate between storage-side and network-side latency, causing candidates to blame the NFS server or jumbo frame misconfiguration when the evidence points to network congestion.
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
✓
Network congestion is causing TCP retransmissions
The most likely cause is network congestion causing TCP retransmissions. When the ESXi host sees high average latency on the NFS datastore but the NFS server reports low latency, it indicates that the delay is occurring in the network path between the host and the server, not on the server itself. TCP retransmissions due to network congestion would cause the host to experience higher latency than the server, matching the symptoms.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Jumbo frames are enabled on the ESXi hosts but not on the NFS server
Why it's wrong here
A jumbo-frame mismatch would cause packet fragmentation or drops, producing failed or retried I/O rather than the sustained high device latency esxtop shows with a healthy NFS server. Jumbo frames are correct when every path device, including switches and the NFS server, shares the same MTU.
- ✓
Network congestion is causing TCP retransmissions
Why this is correct
High latency reported by esxtop on the ESXi side, while the NFS server reports low latency, points to the network path rather than the array. TCP retransmissions from congestion inflate storage latency as packets are resent and responses delayed.
- ✗
The NFS server is performing data deduplication on the datastore
Why it's wrong here
Deduplication runs on the NFS server, so its own reported latency stays low while ESXi's esxtop sees inflated device latency from the added processing delay. It is tempting because deduplication genuinely reduces capacity, but it is chosen for storage efficiency, not for diagnosing network-path latency.
- ✗
The NFS datastore is mounted with read-only permissions
Why it's wrong here
Read-only mounting would block writes outright, producing failed VM operations rather than intermittent latency; the datastore would be unusable for running VMs. It is tempting because permission problems do cause access errors, but read-only is the correct setting for ISO or template repositories, not active VM datastores.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official VMware exam blueprint
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.