FIO Learning

What Is FIO

From gemini

fio (Flexible I/O Tester) is a command-line tool used for benchmarking storage devices and file systems. It provides a flexible and powerful way to measure the performance of disk drives, SSDs, network storage, and other storage systems.

Key Features of fio:

Flexible Workloads: fio supports a wide range of workloads, including sequential, random, read, write, mixed read/write, and various I/O patterns.
Multiple I/O Engines: You can specify different I/O engines, such as direct I/O, buffered I/O, and asynchronous I/O.
Scalability: fio can be used to test a single device or multiple devices simultaneously, enabling scalability for large-scale testing.
Detailed Metrics: It provides comprehensive performance metrics, including IOPS (I/O operations per second), bandwidth, latency, and other statistics.
Script-Based Testing: fio supports scripting, allowing you to automate complex testing scenarios and create custom benchmarks.
Multiple Output Formats: You can choose from various output formats, including plain text, JSON, and XML, for easy analysis.
Platform Support: fio is available on Linux, macOS, and other Unix-like systems.

Uses of fio:

Storage Performance Evaluation: Assessing the performance of disk drives, SSDs, and other storage devices.
File System Benchmarking: Measuring the performance of different file systems, such as ext4, XFS, and ZFS.
Storage System Optimization: Identifying performance bottlenecks and optimizing storage configurations.
Capacity Planning: Determining storage capacity requirements based on expected workloads.
Troubleshooting Performance Issues: Diagnosing and resolving storage-related performance problems.

How to Use fio:

fio is typically run from the command line. Its syntax involves specifying various options, such as:

Job Description: Defining the workload, I/O patterns, and test duration.
Target Device: Specifying the storage device or file system to be tested.
Output Options: Selecting the output format and destination.

Example fio Command:

fio --name=sequential_read --ioengine=libaio --rw=read --bs=4k --iodepth=8 --size=1G --runtime=60

This command performs a sequential read test with a block size of 4 KB, an I/O depth of 8, a total size of 1 GB, and a duration of 60 seconds.

Conclusion:

fio is a powerful and versatile tool for benchmarking and analyzing storage performance. Its flexibility, scalability, and comprehensive metrics make it an indispensable tool for storage engineers, system administrators, and anyone involved in storage performance optimization.

FIO Understanding

I/O Pattern

I/O Engine

Synchronous I/O Engines: For synchronous I/O engines, where each I/O operation waits for acknowledgment before submitting the next one, increasing iodepth beyond 1 won't have any effect.
Asynchronous I/O Engines: In the case of asynchronous I/O engines (which can submit I/O without waiting for acknowledgment), iodepth becomes significant. For example, if you specify an iodepth of 32, up to 32 I/Os can be outstanding before fio waits before submitting more. The actual behavior depends on factors like your operating system, storage, and fio parameters.

https://unix.stackexchange.com/questions/459045/what-exactly-is-iodepth-in-fio 3. Direct IO:

In fio, the term "direct I/O" refers to a mode where the filesystem cache is bypassed, and data is read or written directly between the application and storage. Here are the key points about direct I/O in fio: 1. Purpose: Direct I/O is commonly used for storage performance benchmarking. By avoiding the filesystem cache and memory copy operations, it simplifies storage tests and provides more accurate results. 2. Usage in fio: To enable direct I/O in fio, you can use the --direct=1 option. This corresponds to the O_DIRECT flag on Linux systems. Remember that direct I/O can significantly impact performance testing, especially when evaluating storage systems. 4. Buffered IO:

In fio, buffered I/O is the default mode. Here’s how it works:

Text Only

1. When writing data, fio first copies it into the kernel page cache.
2. Later, the kernel asynchronously flushes this data to disk.
3. Essentially, the data is cached in memory before being written to storage.

> https://buttondown.email/maybematthew/archive/surprising-results-benchmarking-direct-io-vs

This approach is common in most operating systems and provides better performance for certain workloads.

Remember that the choice between buffered and direct I/O impacts performance testing, especially when evaluating storage systems.

I/O Units

The data block size that fio reads or writes to the storage device during a benchmark.

Block Size

The block size in bytes used for I/O units. Default: 4096. A single value applies to reads, writes, and trims. Comma-separated values may be specified for reads, writes, and trims. A value not terminated in a comma applies to subsequent types.

Examples: