CompTIA Linux+ (XK0-006)TroubleshootingEasy
A technician is troubleshooting a server experiencing slow disk I/O. They suspect a particular disk might be bottlenecking performance. Which command and output column would best indicate if a specific disk is consistently busy and potentially causing the bottleneck?
- A`free -h`, looking at the 'available' column for low values.
- B`df -h`, looking at the 'Used%' column for high percentages.
- C`iostat -x 1`, looking at the '%util' column for values near 100%.
- D`top`, looking at the 'wa' (wait) percentage in the CPU summary.
Show answer & explanationAnswer & explanation
Correct answer: C. `iostat -x 1`, looking at the '%util' column for values near 100%.
The `iostat -x 1` command provides extended statistics, and the '%util' column specifically shows the percentage of time the device was busy processing requests. A value near 100% indicates a disk is fully utilized and likely a bottleneck.
Why the other options are wrong
- A. The 'available' column in `free -h` shows available RAM, which is unrelated to disk I/O busyness.
- B. The 'Used%' column in `df -h` shows disk space usage, not I/O activity or busyness.
- D. The 'wa' (wait) percentage in `top` indicates CPU time spent waiting for I/O, but it doesn't pinpoint which *specific* disk is causing the wait or its utilization. `iostat` is more granular for disk-specific issues.
iostat %util
The '%util' column in `iostat` output indicates the percentage of time the device was busy processing I/O requests. High values (near 100%) suggest an I/O bottleneck.
- Measures disk device utilization.
- Values near 100% signify a potential I/O bottleneck.
- Part of `iostat -x` output.
Memory trick: IOSTAT's UTIL column reveals the disk's true toil.