iostat

Overview

The iostat command reports CPU statistics and input/output statistics for devices and partitions. It’s useful for monitoring system input/output device loading.

Syntax

iostat [options] [interval [count]]

Common Options

Option	Description
`-c`	Display CPU utilization
`-d`	Display device utilization
`-h`	Human readable sizes
`-k`	Display in kilobytes
`-m`	Display in megabytes
`-N`	Display registered device mapper names
`-p [device]`	Display statistics for block devices
`-t`	Print time information
`-x`	Display extended statistics
`-y`	Omit first report
`-z`	Omit devices with no activity

Key Use Cases

System performance monitoring
Disk I/O analysis
Bottleneck identification
Capacity planning
Performance tuning

Examples with Explanations

Example 1: Basic Usage

iostat

Show CPU and device statistics

Example 2: Extended Stats

iostat -x 2 5

Show extended stats every 2 seconds, 5 times

Example 3: Device Specific

iostat -p sda 1

Monitor specific device every second

Understanding Output

CPU statistics: - %user: User level processing - %nice: User level with nice priority - %system: System level processing - %iowait: Waiting for I/O - %steal: Time stolen by virtualization - %idle: Idle time

Device statistics: - tps: Transfers per second - kB_read/s: Kilobytes read per second - kB_wrtn/s: Kilobytes written per second - kB_read: Total kilobytes read - kB_wrtn: Total kilobytes written

Common Usage Patterns

Continuous monitoring:
```
iostat 2
```
Specific device analysis:
```
iostat -xd /dev/sda
```
Human readable format:
```
iostat -h -p ALL
```

Performance Analysis

I/O bottleneck detection
Disk utilization patterns
CPU usage correlation
Read/write ratios
Queue length analysis

Additional Resources

Best Practices

Regular monitoring
Baseline establishment
Alert thresholds
Trend analysis
Documentation

Troubleshooting

High wait times
Queue length issues
Bandwidth bottlenecks
Device saturation
CPU bottlenecks