VCP-DCV vSphere Performance and Scaling Practice Question
A company runs a 3-node vSAN cluster with all-flash configuration. Each host has 2 CPUs (8 cores each) and 256 GB RAM. The cluster hosts 30 VMs, including a critical database VM with 8 vCPUs and 64 GB RAM. Recently, users report that the database VM is slow during peak hours. The administrator checks vCenter performance charts and sees that the VM's CPU ready time averages 10%, and the vSAN latency spikes to 15 ms during peak hours. The storage policy for the database VM is set to RAID-1 mirroring with 2 failures to tolerate (FTT=2). The cluster is configured with 3 disk groups per host, each with one 400 GB NVMe cache SSD and two 2 TB SAS SSD capacity drives. Which action would most improve the performance of the database VM?
⚠ Common exam trap
The trap here is that candidates often focus on adding hardware (disk groups or hosts) to solve performance issues, overlooking that the storage policy's replication factor (FTT) directly controls write amplification and is the root cause of both CPU ready time and vSAN latency spikes.
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
✓
Change the storage policy for the database VM to RAID-1 mirroring with FTT=1 (primary level of failures to tolerate).
The database VM is experiencing high CPU ready time (10%) and vSAN latency spikes (15 ms). With FTT=2 and RAID-1 mirroring, each write must be replicated to three hosts (the primary and two mirrors), consuming significant storage and network resources. Reducing FTT to 1 lowers the write amplification from 3x to 2x, decreasing I/O latency and freeing up CPU cycles for the VM, directly addressing both 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.
- ✗
Add one additional disk group to each host to increase storage performance.
Why it's wrong here
Incorrect: Adding disk groups can improve parallelism but does not directly reduce the overhead from FTT=2.
- ✓
Change the storage policy for the database VM to RAID-1 mirroring with FTT=1 (primary level of failures to tolerate).
Why this is correct
Correct: Reducing FTT from 2 to 1 reduces the number of replicas from 3 to 2, decreasing write amplification and latency.
- ✗
Remove one host from the cluster to reduce network traffic.
Why it's wrong here
Incorrect: Removing a host would reduce fault tolerance and may cause data unavailability.
- ✗
Add a fourth host to the vSAN cluster to distribute the load.
Why it's wrong here
Incorrect: Adding a host may help with capacity but not directly with latency; the cluster already meets minimum requirements.
Quick reference
RAID Level Comparison
| RAID Level | Min Disks | Fault Tolerance | Read | Write | Usable Capacity |
|---|---|---|---|---|---|
| RAID 0 | 2 | None | Excellent | Excellent | 100% |
| RAID 1 | 2 | 1 disk | Good | Moderate | 50% |
| RAID 5 | 3 | 1 disk | Good | Moderate | 67–94% |
| RAID 6 | 4 | 2 disks | Good | Lower | 50–88% |
| RAID 10 | 4 | 1 disk per mirror | Excellent | Good | 50% |
RAID is not a backup strategy — it protects against disk failure but not against accidental deletion, ransomware, or site-level events.
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JA
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.