SK0-005 troubleshooting Practice Question
Exhibit
[ 234.567890] sd 0:0:0:0: [sda] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 234.567895] sd 0:0:0:0: [sda] tag#0 Sense Key : Medium Error [current] [ 234.567899] sd 0:0:0:0: [sda] tag#0 Add. Sense: Unrecovered read error - auto reallocate failed [ 234.567903] sd 0:0:0:0: [sda] tag#0 CDB: Read(10) 28 00 00 00 00 00 00 00 08 00 [ 234.567906] blk_update_request: I/O error, dev sda, sector 12345678
Refer to the exhibit. A Linux server started reporting I/O errors to its local disk. The administrator runs `dmesg` and sees the output shown. Which of the following is the MOST likely cause of the errors?
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
✓
The disk has a bad sector that cannot be remapped.
Option B is correct. The 'Medium Error' sense key along with 'Unrecovered read error - auto reallocate failed' indicates a physical bad sector that the drive could not reallocate. Option A would typically produce a different hostbyte (e.g., DID_NO_CONNECT). Option C, outdated firmware, rarely causes medium errors. Option D, filesystem corruption, would manifest as filesystem-level errors, not SCSI sense codes.
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 disk has a bad sector that cannot be remapped.
Why this is correct
The Sense Key 'Medium Error' and additional sense 'auto reallocate failed' explicitly indicate an unreadable sector that the drive's internal remapping could not fix.
- ✗
The filesystem on /dev/sda is corrupted.
Why it's wrong here
Filesystem corruption leads to errors like 'Input/output error' at the OS level, but the dmesg output here shows a low-level SCSI read error, not a filesystem issue.
- ✗
The SCSI cable is loose.
Why it's wrong here
A loose cable would more likely result in transport errors (hostbyte=DID_NO_CONNECT or DID_BAD_TARGET), not a Medium Error from the drive itself.
- ✗
The RAID controller firmware is outdated.
Why it's wrong here
Firmware issues do not typically generate 'Medium Error' sense codes; they would more likely cause driver or communication errors.
Go deeper
Related to this question
Learn chapter
Physical and Logical Security Controls
Key term
Firmware
Firmware is specialized software permanently stored in read-only memory on a hardware device that controls how that device operates at a basic level.
Key term
dmesg
dmesg is a Linux command that displays messages from the kernel ring buffer, used to diagnose hardware and boot issues.
About these practice questions
One of 185 original SK0-005 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed July 2026 · checked against the official CompTIA exam blueprint
This SK0-005 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 SK0-005 exam.