iotop: Disk I/O Usage Monitoring

Overview

iotop displays real-time disk I/O activity, allowing you to see in detail how much disk read/write each process or thread is performing. This helps in analyzing the causes of system performance degradation and understanding the disk usage patterns of specific applications.

Key Features

Real-time I/O monitoring per process/thread
Display of total disk read/write speeds
Hide processes with no I/O activity
View cumulative I/O statistics

Key Options

The main options for iotop help control the output format and focus on specific information.

Display/Filtering

Execution Control

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Usage Examples

Various ways to monitor disk I/O activity using iotop.

Basic I/O Monitoring

sudo iotop

Displays real-time I/O usage for all processes/threads.

Show Only Processes with I/O Activity

sudo iotop -o

Filters and shows only processes/threads currently performing disk I/O.

Show Processes Only (Exclude Threads)

sudo iotop -P

Displays I/O usage on a per-process basis, excluding thread information.

Display Cumulative I/O Statistics

sudo iotop -ao

Shows the cumulative I/O total since iotop was run, instead of real-time speeds.

Update Every 3 Seconds

sudo iotop -d 3

Monitors with a screen update interval set to 3 seconds.

Installation

iotop is not included by default in most Linux distributions, so it needs to be installed via a package manager.

Debian/Ubuntu

sudo apt update
sudo apt install iotop

Installs iotop using the APT package manager.

CentOS/RHEL/Fedora

sudo yum install iotop  # or dnf install iotop

Installs iotop using the YUM or DNF package manager.

Tips & Notes

Tips and points to note for effective use of iotop.

Interpreting I/O Activity

iotop's output shows the disk read/write speeds of each process through the 'READ' and 'WRITE' columns. 'SWAPIN' indicates swap space usage, and 'IO' represents disk I/O wait time. High values may suggest disk bottlenecks.

READ/WRITE: Disk read/write speed per second
SWAPIN: Swap-in activity ratio
IO: I/O wait time ratio (time the process spends waiting for I/O)

Root Privileges Required

iotop generally requires root privileges to monitor all system I/O activity. Therefore, it is commonly run with sudo.

Performance Impact

iotop itself uses some system resources (especially CPU). Running it for extended periods on very busy systems or setting very short update intervals can have a minor impact on system performance.