How to Monitor Disk I/O

Prerequisites

Before monitoring disk I/O, make sure you have:

• SSH access to your VPS
• Root or sudo privileges (for some tools)

Method 1: Using iostat (System Statistics)

Connect to your VPS:

ssh hxroot@YOUR_SERVER_IP -p 22

Install sysstat:

apt install sysstat -y

Run iostat:

iostat -x 2

Key columns to watch:

• %util – Percentage of time disk is busy (high = bottleneck)
• await – Average time for I/O requests (ms)
• r/s, w/s – Reads/writes per second
• rkB/s, wkB/s – Kilobytes read/written per second

Method 2: Using iotop (Per-Process I/O)

apt install iotop -y

sudo iotop

Shows real-time I/O activity by process. Press q to quit.

Method 3: Using dstat (Combined View)

apt install dstat -y

dstat -d -r

Shows disk reads/writes and I/O statistics.

Method 4: Using vmstat (I/O Wait)

vmstat 2 5

Look at the wa column – high values indicate processes waiting for disk I/O.

Method 5: Using ioping (Latency Test)

apt install ioping -y

ioping -c 10 /var

Measures disk latency similar to ping.

Find Processes Causing High I/O

sudo iotop -b -n 1 | head -20

Or using ps:

ps aux | awk '{if($8=="D") print}'

Processes in "D" state (uninterruptible sleep) are often waiting for I/O.

Monitor I/O Over Time (Simple Script)

#!/bin/bash
while true; do
    clear
    echo "=== Disk I/O at $(date) ==="
    iostat -x 1 1 | grep -A 1 "Device"
    sleep 2
done