220-1101 Virtualization and Cloud Computing Practice Question
A system administrator is configuring a virtual machine (VM) on a VMware ESXi host. The VM runs a critical database application that requires a guaranteed minimum amount of memory to perform well. The host has memory overcommitment enabled. Which setting should the administrator configure to ensure the VM always has at least 4 GB of physical memory available?
⚠ Common exam trap
Watch out — candidates often confuse a memory reservation (guaranteed minimum) with a memory limit (maximum ceiling), leading candidates to incorrectly select limit when the question explicitly asks for a guaranteed minimum.
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
✓
Memory reservation
A memory reservation guarantees that the ESXi host will allocate at least the specified amount of physical memory to the VM, even when memory overcommitment is enabled. This ensures the critical database application always has a minimum of 4 GB of physical RAM available, preventing performance degradation due to contention.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Memory reservation
Why this is correct
A memory reservation guarantees the VM will always have that specified amount of physical host memory available to it, regardless of memory pressure on the host. The hypervisor immediately sets aside that memory when the VM powers on, preventing other VMs from consuming it. This ensures predictable performance and is essential for VMs running latency-sensitive or critical workloads.
- ✗
Memory limit
Why it's wrong here
A memory limit defines the maximum amount of memory the VM is permitted to consume, but it does not set any minimum guarantee regarding physical memory allocation. When the limit is reached, the hypervisor will reclaim memory from the VM, potentially causing the guest OS to swap or balloon. This serves as a control mechanism to prevent a VM from monopolizing host resources, yet it provides no assurance that the VM will receive enough memory to perform optimally.
When this WOULD be correct
A memory limit would be correct when the administrator needs to prevent a VM from consuming more than a specified amount of memory, such as to control resource usage or avoid impacting other VMs on the host.
- ✗
Memory ballooning
Why it's wrong here
Memory ballooning is an active hypervisor technique used to reclaim memory from a VM when the host is under memory pressure, by forcing the guest OS to allocate extra memory pages via a balloon driver that is inflated to increase guest memory pressure. The guest then swaps its own pages to disk, freeing up host memory for other VMs. This process does not guarantee memory to a VM; instead, it can actually reduce the VM's available physical memory and cause performance degradation.
When this WOULD be correct
An administrator needs to reclaim unused memory from idle VMs to improve overall host memory utilization without impacting performance of active VMs. Memory ballooning would be the correct technique to gently reclaim memory from VMs that are not using their allocated memory.
- ✗
Swap file size
Why it's wrong here
The swap file size represents the amount of virtual memory that the hypervisor may exchange to disk when a VM's memory is overcommitted, but it does not guarantee any physical memory allocation to the VM. It is calculated as the difference between the VM's configured memory and its reservation, so a larger swap file indicates a greater buffer for host memory reclamation, not a memory guarantee. This file is used as a backing store for pages that are swapped out under contention, but its existence does not ensure the VM has enough physical RAM.
When this WOULD be correct
A VM is experiencing performance issues due to insufficient swap space, and the administrator needs to ensure the VM has enough swap file capacity to handle memory pressure without crashing.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓Memory reservationCorrect answer▾
Why this is correct
A memory reservation guarantees the VM will always have that specified amount of physical host memory available to it, regardless of memory pressure on the host. The hypervisor immediately sets aside that memory when the VM powers on, preventing other VMs from consuming it. This ensures predictable performance and is essential for VMs running latency-sensitive or critical workloads.
✗Memory limitWrong answer — click to see why▾
Why this is wrong here
A memory limit caps the maximum memory a VM can use, but does not guarantee a minimum amount of physical memory. In this scenario, the administrator needs to ensure at least 4 GB is always available, which is achieved by setting a reservation, not a limit.
★ When this WOULD be the correct answer
A memory limit would be correct when the administrator needs to prevent a VM from consuming more than a specified amount of memory, such as to control resource usage or avoid impacting other VMs on the host.
Why candidates choose this
Candidates may confuse 'limit' with 'reservation' because both are memory controls, but they serve opposite purposes: a limit caps usage, while a reservation guarantees availability.
✗Memory ballooningWrong answer — click to see why▾
Why this is wrong here
Memory ballooning is a mechanism for reclaiming memory from VMs by inflating a balloon driver, but it does not guarantee a minimum amount of physical memory; it actually reduces the VM's available memory under host pressure.
★ When this WOULD be the correct answer
An administrator needs to reclaim unused memory from idle VMs to improve overall host memory utilization without impacting performance of active VMs. Memory ballooning would be the correct technique to gently reclaim memory from VMs that are not using their allocated memory.
Why candidates choose this
Candidates may confuse memory ballooning with memory reservation because both involve memory management in overcommitted environments, and 'ballooning' sounds like it could ensure memory availability.
✗Swap file sizeWrong answer — click to see why▾
Why this is wrong here
Swap file size determines the amount of disk space used for swapping when memory is overcommitted, but it does not guarantee a minimum amount of physical memory for a VM. The setting to guarantee physical memory is memory reservation.
★ When this WOULD be the correct answer
A VM is experiencing performance issues due to insufficient swap space, and the administrator needs to ensure the VM has enough swap file capacity to handle memory pressure without crashing.
Why candidates choose this
Candidates may confuse swap file size with memory reservation, thinking that increasing swap space guarantees physical memory availability, or they may believe swap file size directly controls memory allocation.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
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Key term
Dual In-line Memory Module
A Dual In-line Memory Module (DIMM) is a small circuit board that holds memory chips and plugs into a computer's motherboard to provide Random Access Memory (RAM).
Key term
RAM
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA 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 220-1101 exam.