The correct answer is that the LUN presenting the virtual disk is not zoned or masked to the backup server. This is because the error message indicates the backup server cannot access the storage resource, and in SAN environments, LUN masking and zoning are the primary controls that govern which servers can see and connect to specific storage volumes; a misconfiguration here directly blocks the backup job. On the CISA exam, this scenario tests your understanding of storage area network (SAN) security and access controls, often appearing as a trap where candidates mistakenly blame network connectivity or backup software settings. Remember the key distinction: zoning operates at the Fibre Channel switch level, while LUN masking is done at the storage array—both must align for successful backup access. A helpful memory tip is “Zone the path, mask the disk; if backup fails, check the link.”
CISA Practice Question: Information Systems Operations and Business Resilience
This CISA practice question tests your understanding of information systems operations and business resilience. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Refer to the exhibit.
```
ERROR: 2019-10-22 14:23:45.678
Severity: CRITICAL
Source: BackupServer1
Message: Backup job 'FinanceDB_Full' failed.
Reason: Unable to mount virtual disk 'FinData-001' from storage array 'SAN01'.
Suggested action: Check storage array connectivity and LUN masking.
```
Refer to the exhibit. An IT operator receives this error message from an automated backup job. What is the MOST likely cause of this failure?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The LUN presenting the virtual disk is not zoned or masked to the backup server
Option D is correct because the error indicates that the backup server cannot access the virtual disk, which is typically a LUN masking or zoning issue. Option A is plausible but the message specifically points to storage access; Option B is not indicated; Option C is possible but less direct.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The FinanceDB database is corrupted
Why it's wrong here
The error is at the storage level, not database level.
✗
The network link between servers is down
Why it's wrong here
The error states 'storage array connectivity', which may include network but is more specific to SAN.
✗
The backup server's disk is full
Why it's wrong here
The error is about mounting a source volume, not storing the backup.
✓
The LUN presenting the virtual disk is not zoned or masked to the backup server
Why this is correct
The error 'Unable to mount virtual disk' strongly suggests a SAN zoning/LUN masking issue.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CISA subnetting questions on CIDR, address ranges, and subnet selection.
Information Systems Operations and Business Resilience — This question tests Information Systems Operations and Business Resilience — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The LUN presenting the virtual disk is not zoned or masked to the backup server — Option D is correct because the error indicates that the backup server cannot access the virtual disk, which is typically a LUN masking or zoning issue. Option A is plausible but the message specifically points to storage access; Option B is not indicated; Option C is possible but less direct.
What should I do if I get this CISA question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CISA subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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