Cheatsheet & Examples: iostat

Cheatsheet & Examples: iostat

iostat is a command-line tool used to monitor system input/output (I/O) statistics, including CPU utilization and disk activity. It provides insights into disk read/write speeds, I/O queue lengths, and device performance.

Display Overall System I/O Statistics

Example Usage: iostat

What it does: Shows a summary of CPU and disk I/O statistics for the entire system. The output includes average values over the time since the last boot.

Command-line Arguments Explained:

None: The command runs with default options, displaying system-wide I/O data.

Monitor I/O Statistics at Intervals

Example Usage: iostat 1 5

What it does: Displays I/O statistics at 1-second intervals for 5 iterations, allowing real-time observation of disk and CPU activity.

Command-line Arguments Explained:

1: Interval in seconds between updates.
5: Number of iterations (updates) to display.

Show Disk I/O Statistics Only

Example Usage: iostat -d

What it does: Focuses on disk I/O statistics, omitting CPU utilization details.

Command-line Arguments Explained:

-d: Disables CPU statistics and shows only disk-related data.

Display Extended Disk I/O Statistics

Example Usage: iostat -x

What it does: Provides detailed disk I/O statistics, such as average request size, I/O wait time, and service time.

Command-line Arguments Explained:

-x: Enables extended statistics for disks, offering more in-depth metrics.

Monitor Specific Disks or Devices

Example Usage: iostat -d sda sdb

What it does: Displays I/O statistics for the specified disks (sda, sdb) instead of all devices.

Command-line Arguments Explained:

-d: Shows disk statistics.
sda sdb: Specifies one or more disk device names (e.g., sda, sdb).

Use Custom Units for I/O Metrics

Example Usage: iostat -m 2

What it does: Displays I/O statistics in megabytes (MB) instead of kilobytes (KB) or bytes, with updates every 2 seconds.

Command-line Arguments Explained:

-m: Display I/O statistics in megabytes (MB) rather than kilobytes (KB).
2: Interval in seconds between updates.

Include Timestamps in Output

Example Usage: iostat -t 1

What it does: Displays I/O statistics at 1-second intervals, with timestamps added to each output line.

Command-line Arguments Explained:

-t: Displays timestamps for each I/O statistics update.

Show Device Names Instead of Major/Minor Numbers

Example Usage: iostat -N

What it does: Replaces device major/minor numbers with human-readable device names in the output.

Command-line Arguments Explained:

-N: Displays device names (e.g., /dev/sda) instead of numerical identifiers.

Monitor CPU Utilization Only

Example Usage: iostat -c

What it does: Focuses on CPU utilization statistics, omitting disk I/O details.

Command-line Arguments Explained:

-c: Displays CPU utilization statistics instead of disk I/O data.

Show Per-Partition Disk I/O Statistics

Example Usage: iostat -d -p 1

What it does: Reveals I/O statistics for individual disk partitions (e.g., sda1, sda2) at 1-second intervals.

Command-line Arguments Explained:

-d: Shows disk statistics.
-p: Displays I/O statistics for each partition of the disk.