Analyze Disk I/O with iostat -x

iostat -x prints extended per-device statistics — r/s, w/s, await, and %util — refreshed on an interval so you can watch saturation.

LinuxperformancediskiostatLow risk

Run `iostat -x 2 5` to sample extended disk statistics every 2 seconds, 5 times, and look at %util and await to find a saturated or slow disk.

01Command

Command

$ iostat -x 2 5

02What it does

Plain `iostat` shows only coarse transfer totals; the -x flag is what reveals the useful per-device columns. await is the average request wait time in ms (a spinning drive with await consistently above ~15 ms is a red flag), and %util approaches 100% when a device is saturated. The first report is a since-boot average, so ignore it and read the interval samples; add `-d` to drop the CPU table or `-k`/`-m` for unit control.

03Risk

RiskLow risk

Requirementssysstat package (apt install sysstat / dnf install sysstat).

04Undo

✓No undo needed — this command does not change persistent state.

05Sources

iostat(1) - Report CPU statistics and I/O statistics for devices
Ubuntu Manpages · technical · 2026-09-17
Evidence: -x shows extended statistics; interval and count parameters report repeatedly; %util is the percentage of elapsed time during which the device was busy.

Last verified: 2026-09-17 · Category: System & Settings

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