mediumMultiple ChoiceObjective-mapped
CISA Practice Question: An organization's online transaction processing…
An organization's online transaction processing system experienced a sudden performance degradation. The database administrator checked system resources and found excessive I/O wait time on the storage subsystem. Which of the following is the MOST likely root cause?
⚠ Common exam trap
A common mix-up: candidates confuse I/O wait with general performance issues and incorrectly attribute it to SQL inefficiency or memory pressure, but the question specifically isolates the symptom to the storage subsystem, making a storage-level bottleneck the most direct and likely root cause.
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
✓
Inadequate disk spindles or a storage area network (SAN) bottleneck
Excessive I/O wait time directly indicates that the storage subsystem is the bottleneck, not the database server's CPU or memory. Inadequate disk spindles or a SAN bottleneck (e.g., insufficient HBA queue depth, oversubscribed SAN links, or slow RAID rebuilds) cause the storage layer to become saturated, forcing the OS to wait for I/O completions. This is the most likely root cause because the symptom is specifically I/O wait, not CPU or memory pressure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
An inefficient SQL query causing table scans
Why it's wrong here
Inefficient queries can increase I/O, but the root cause is still the storage performance; however, the question asks for the most likely root cause, and without evidence of query issues, storage bottleneck is more direct.
- ✓
Inadequate disk spindles or a storage area network (SAN) bottleneck
Why this is correct
I/O wait is a clear indicator of storage subsystem saturation, often due to insufficient disk spindles or SAN performance issues.
- ✗
Insufficient memory allocated to the database server
Why it's wrong here
Insufficient memory leads to swapping, which increases paging activity, but the primary symptom is high paging, not I/O wait directly.
- ✗
Network latency between the application and database servers
Why it's wrong here
Network latency would show as network-related delays, not disk I/O wait.
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
About these practice questions
Courseiva writes every CISA question from scratch — 995 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISA practice question is part of Courseiva's free ISACA 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 CISA exam.