Iostat & SAR System Statistics

Iostat - Install

# Ubuntu/Debian
sudo apt install sysstat

# Enable data collection
sudo systemctl enable sysstat
sudo systemctl start sysstat

Basic iostat

iostat

Extended statistics

iostat -x

Show in MB/s

iostat -m

Specific device

iostat -x sda

Continuous monitoring (every 2s)

iostat -x 2

Monitor 5 times, every 2s

iostat -x 2 5

CPU statistics only

iostat -c

Disk statistics only

iostat -d

Human readable

iostat -h

Include partition stats

iostat -p sda

NFS statistics

iostat -n

Important iostat metrics

%util     # Device utilization (100% = saturated)
await     # Average wait time (ms)
svctm     # Service time (deprecated)
r/s       # Reads per second
w/s       # Writes per second
rkB/s     # KB read per second
wkB/s     # KB written per second

SAR - Basic usage

sar

CPU usage (current)

sar -u 1 5

CPU usage (all cores)

sar -P ALL 1 5

Memory usage

sar -r 1 5

Swap usage

sar -S 1 5

Disk I/O

sar -d 1 5

Network statistics

sar -n DEV 1 5

Network errors

sar -n EDEV 1 5

Load average

sar -q 1 5

Context switches

sar -w 1 5

Paging statistics

sar -B 1 5

View historical data

sar -f /var/log/sysstat/sa$(date +%d)

Historical CPU

sar -u -f /var/log/sysstat/sa15

Historical for specific time

sar -u -s 10:00:00 -e 11:00:00

Historical for date

sar -u -f /var/log/sysstat/sa15 -s 14:00:00 -e 15:00:00

All statistics

sar -A

Export to file

sar -u 1 10 -o /tmp/sar_data

Read from file

sar -u -f /tmp/sar_data

Network device stats

sar -n DEV,EDEV 1 5

TCP statistics

sar -n TCP 1 5

Socket statistics

sar -n SOCK 1 5

Important SAR metrics

%user     # User CPU time
%system   # System CPU time
%iowait   # Waiting for I/O
%idle     # Idle CPU time
kbmemfree # Free memory
kbswpfree # Free swap
tps       # Transfers per second
rxkB/s    # KB received per second
txkB/s    # KB transmitted per second

Analyze high I/O wait

# Check overall CPU
sar -u 1 5

# Check disk I/O
sar -d 1 5

# Check individual disks
iostat -x 1 5

# Find processes
iotop

SAR report for yesterday

sar -u -f /var/log/sysstat/sa$(date -d yesterday +%d)

Generate daily report

# Ubuntu/Debian
/usr/lib/sysstat/sa2

SAR configuration

Edit /etc/default/sysstat:

ENABLED="true"

SAR data retention

Edit /etc/sysstat/sysstat:

HISTORY=30

Cron schedule

cat /etc/cron.d/sysstat

Real-time monitoring script

#!/bin/bash
while true; do
    clear
    echo "=== CPU ==="
    sar -u 1 1 | tail -1
    echo ""
    echo "=== Memory ==="
    sar -r 1 1 | tail -1
    echo ""
    echo "=== Disk I/O ==="
    iostat -x 1 1 | grep -E "sda|nvme"
    sleep 2
done