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220-1201 Practice Question: A technician is configuring a virtual machine to…
A technician is configuring a virtual machine to host a database server that requires consistent high disk I/O performance. The host uses a RAID 10 array of SSDs. Which virtual disk type should the technician select to minimize overhead and maximize performance?
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
✓
Fixed-size virtual disk
A fixed-size virtual disk (also called thick provisioning) allocates all required space at creation, reducing fragmentation and I/O overhead compared to dynamically expanding disks. This is best for performance-sensitive workloads like databases.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Dynamically expanding virtual disk
Why it's wrong here
Dynamically expanding virtual disks grow in size only as data is written, starting with a small footprint. This on-demand allocation often results in non-contiguous blocks being written to the host's physical storage, leading to increased fragmentation. The continuous need for the hypervisor to allocate new blocks and update metadata introduces significant I/O overhead and latency, making them unsuitable for performance-critical applications like databases that require consistent, fast disk access.
- ✓
Fixed-size virtual disk
Why this is correct
A fixed-size virtual disk allocates its entire specified capacity on the host storage at the time of creation. This pre-allocation ensures that the virtual disk occupies contiguous blocks on the physical storage, minimizing fragmentation and reducing the overhead associated with dynamic allocation. This design significantly lowers I/O latency and improves read/write performance, making it the optimal choice for applications like databases that demand consistent, high-speed disk operations.
- ✗
Differencing virtual disk
Why it's wrong here
Differencing disks store only the changes made to a parent virtual disk, creating a chain of disks where each child disk references its parent. While useful for testing, snapshots, or VDI environments, every read or write operation requires traversing the entire chain to find the correct block. This introduces substantial I/O overhead and latency, making them highly inefficient and detrimental to the performance required by production database servers.
- ✗
Thin provisioned virtual disk
Why it's wrong here
Thin provisioning allows a virtual disk to be presented with a larger capacity than it physically consumes on the storage array, allocating physical space only as data is written. Although efficient for storage utilization, this on-demand allocation process can introduce performance penalties similar to dynamically expanding disks. The hypervisor or storage array must constantly manage and allocate new physical blocks, potentially leading to fragmentation and increased I/O latency, which is undesirable for demanding database workloads.
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.
Go deeper
Related to this question
Learn chapter
Troubleshoot: Storage and RAID
Key term
Virtual machine
A virtual machine (VM) is a software-based emulation of a physical computer that runs an operating system and applications just like a real machine, but is isolated and managed by a hypervisor on a host system.
Key term
RAID 10
RAID 10 combines RAID 1 mirroring and RAID 0 striping to provide both high performance and fault tolerance by writing identical data across mirrored pairs that are then striped for speed.
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Same concept, more angles
1 more way this is tested on 220-1201
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Variation 1. A technician needs to deploy a virtual machine that will be used for a short-term project and then deleted. The VM must not consume excessive storage space initially. Which virtual disk type should be chosen?
hard- A.Fixed-size (thick) virtual disk
- B.Differencing disk
- ✓ C.Thin-provisioned virtual disk
- D.Dynamic expanding disk
Why C: The provided explanation accurately describes the behavior of a thin-provisioned disk, which is correct. However, this description also applies to a dynamic expanding disk, reinforcing the ambiguity between options C and D.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1201 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 220-1201 exam.