💡 Performance & Debugging September 1, 2026 2

Linux Command: iostat

Report CPU and I/O statistics

Terminal — Performance & Debugging

Command

$ iostat -x 1

Output

Device r/s w/s rkB/s wkB/s await %util sda 10.5 25.3 420.0 1012.0 2.5 15.3

iostat reports CPU and I/O statistics for devices and partitions. It is the primary tool for monitoring disk I/O performance, identifying bottlenecks, and measuring throughput. iostat shows read/write speeds, I/O operations per second (IOPS), average queue sizes, and service times. This data is essential for diagnosing slow disk performance. iostat is part of the sysstat package and is commonly used alongside vmstat and sar for comprehensive system monitoring.

Syntax

iostat [OPTION]... [DEVICE] [INTERVAL]

Key Options

-x — Extended statistics
-d — Device statistics only
-c — CPU statistics only
-h — Human-readable
-p — Include partitions
N — Update interval in seconds

Examples

Extended I/O stats

iostat -x 1

Output: Device r/s w/s rkB/s wkB/s await %util sda 10.5 25.3 420.0 1012.0 2.5 15.3

Device stats only

iostat -d 2

Human-readable

iostat -dh 1

Pro Tips

%util >70% means device is busy. await >10ms on SSD = problem. r/s and w/s show IOPS.
Install with: apt install sysstat or yum install sysstat.
Like vmstat, the first report shows averages since boot. Subsequent reports show current values.

Learn more: Full iostat reference →