Detailed explanation of Linux disk I/O and introduction to common commands

What is disk I/O

Disk I/O refers to data input and output operations between the computer system and the hard disk (disk).

This includes reading data from disk (input) and writing data to disk (output).

In the Linux operating system, disk I/O involves reading and writing files, including file system operations and data exchange.

Commonly used disk I/O commands

1.iostat

iostatThe command is used to display CPU usage and disk I/O statistics.

It helps you monitor disk activity on your system.

Example: Useiostatto view disk I/O statistics

iostat

This example will display disk I/O statistics on the current system, including read and write speeds for each disk, average response time, etc.

2.iotop

iotopThe command is an interactive tool for monitoring disk I/O activity in real time and showing which processes are performing disk operations.

Example: Useiotopto monitor disk I/O activity in real time

iotop

This example will open the real-time monitoring interface ofiotopto display the disk I/O activity of each process.

3.dd

ddcommand is a powerful command line tool for copying files and devices, and performing disk I/O performance testing.

Example: Useddto copy files

dd if=input_file of=output_file bs=4K count=1000

This example will copy 1000 blocks (4KB each) frominput_filetooutput_file.

4.hdparm

hdparmThe command is used to configure and display the parameters of the hard drive and test the hard drive performance.

Example: Usehdparmto view hard disk information

hdparm -I /dev/sda

This example will display the details of the/dev/sdahard drive, including supported features and parameters.

5.smartctl

smartctlThe command is used to monitor and analyze the Self-Monitoring Analysis and Reporting Technology (SMART) data of the hard disk to detect hard disk problems and failures.

Example: Usesmartctlto view hard disk SMART data

smartctl -a /dev/sda

This example will display SMART data for the/dev/sdahard drive, including various health indicators and error rates.

syncCommand

synccommand is used to force the data in the file system buffer to be written to the disk to ensure the persistence of the data.

This is important to ensure file system consistency, especially after important file operations.

Example: Use thesynccommand to synchronize data

sync

This example will force the data in the file system buffer to be written to disk.

fioTools

fio(Flexible I/O Tester) is a powerful tool for flexible disk I/O performance testing.

It can simulate various read and write operations to evaluate disk performance.

Example: Usingfiofor disk performance testing

First, you need to install thefiotool. You can then create a file containing the test configuration, such asmy_test.fio:

[global] ioengine=libaio direct=1 size=1G rw=randread numjobs=4

Next, run the test:

fio my_test.fio

This example will perform a random read (randread) performance test, using 4 jobs (jobs) and reading 1GB of data.

Disk I/O Optimization and Troubleshooting

Understanding disk I/O not only helps monitor system performance, but also helps optimize and troubleshoot.

Here are some common optimization and troubleshooting suggestions:

• Use RAID arrays to improve performance and redundancy.
• Regularly clean unnecessary files and logs to free up disk space.
• Monitor hard drive SMART data to detect potential hardware problems.
• Avoid frequent small file write operations and can be processed in batches to reduce disk overhead.
• Use an appropriate file system such as ext4 or XFS, adjusting as needed.
• Use disk caching and write buffering to improve performance.

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