VCP-DCV vSphere Performance and Scaling Practice Question
A vSphere administrator is designing a new cluster for a workload that requires high memory bandwidth and low latency. The physical hosts have 512 GB of RAM each, and the VMs are expected to have large memory footprints. The administrator wants to ensure that memory overcommitment is minimized and that VM memory is backed by physical RAM as much as possible. Which configuration should be applied to the VMs to achieve this?
⚠ Common exam trap
Candidates often confuse memory limits with reservations; limits cap usage but do not guarantee physical RAM allocation, while reservations do.
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
✓
Set a memory reservation equal to the configured memory size for each VM.
Setting a memory reservation equal to the VM's configured memory size ensures that all of the VM's memory is backed by physical RAM, preventing overcommitment and guaranteeing low-latency memory access. This is the most direct way to meet the requirement for high memory bandwidth and minimal overcommitment.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure the VM to use large memory pages and set a memory reservation of 50% of the configured memory.
Why it's wrong here
Large memory pages can improve memory access efficiency, but a reservation of only 50% still allows the remaining memory to be overcommitted. This does not ensure that all VM memory is backed by physical RAM. The workload requires minimal overcommitment, so a partial reservation is insufficient to meet the low-latency and high-bandwidth requirements.
- ✓
Set a memory reservation equal to the configured memory size for each VM.
Why this is correct
A memory reservation guarantees that the specified amount of physical RAM is reserved for the VM. Setting it equal to the configured memory size ensures that the VM's entire memory is backed by physical RAM, eliminating memory overcommitment for that VM. This provides predictable performance and low latency, which is critical for high-bandwidth workloads.
- ✗
Set a memory limit equal to the configured memory size and enable memory ballooning.
Why it's wrong here
A memory limit does not reserve physical RAM; it only caps the VM's memory usage. Enabling ballooning allows the hypervisor to reclaim memory from the VM, which can increase latency and reduce performance. This configuration is the opposite of what is needed for a low-latency, high-bandwidth workload, as it introduces memory reclamation overhead.
- ✗
Enable memory compression and set a memory limit equal to the configured memory size.
Why it's wrong here
Memory compression reduces the impact of overcommitment by compressing idle memory pages, but it does not guarantee that all VM memory resides in physical RAM. A memory limit caps the VM's memory usage but does not reserve physical RAM. This combination does not prevent overcommitment; it only manages it after the fact, which is not suitable for low-latency requirements.
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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
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