Benchmarking USB Drives with Shell Scripts – Part 1: Why I Built a Benchmark Script

Introduction

When I upgraded from an old 8GB USB stick to a shiny new 256GB one, I expected faster speeds and more convenience—especially for carrying around multiple bootable ISO files using Ventoy. With modern Linux distributions often exceeding 4GB per ISO, my old drive could barely hold a single image. But I quickly realized that storage space was only half the story—performance matters too.

Curious about how much of an upgrade I had actually made, I decided to benchmark the read speed of both USB sticks. Instead of hunting down benchmarking tools or manually comparing outputs, I turned to ChatGPT to help me craft a reliable, repeatable shell script that could automate the entire process. In this post, I’ll share how ChatGPT helped me go from an idea to a functional USB benchmark script, and what I learned along the way.

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The Goal

I wanted to answer a few simple but important questions:

• How much faster is my new USB stick compared to the old one?
• Do different USB ports affect read speeds?
• How can I automate these tests and compare the results?

But I also wanted a reusable script that would:

• Detect the USB device automatically
• Find or use a test file on the USB stick
• Run several types of read benchmarks
• Present the results clearly, with support for summary and CSV export

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Getting Help from ChatGPT

I asked ChatGPT to help me write a shell script with these requirements. It guided me through:

• Choosing benchmarking tools: hdparm, dd, pv, ioping, fio
• Auto-detecting the mounted USB device
• Handling different cases for user-provided test files or Ubuntu ISOs
• Parsing and converting human-readable speed outputs
• Displaying results in human-friendly tables and optional CSV export

We iterated over the script, addressing edge cases like:

• USB devices not mounted
• Multiple USB partitions
• pv not showing output unless stderr was correctly handled
• Formatting output consistently across tools

ChatGPT even helped optimize the code for readability, reduce duplication, and handle both space-separated and non-space-separated speed values like “18.6 MB/s” and “18.6MB/s”.

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Benchmark Results

With the script ready, I ran tests on three configurations:

1. Old 8GB USB Stick

hdparm       16.40 MB/s
dd           18.66 MB/s
dd + pv      17.80 MB/s
cat + pv     18.10 MB/s
ioping        4.44 MB/s
fio          93.99 MB/s

2. New 256GB USB Stick (Fast USB Port)

hdparm      372.01 MB/s
dd          327.33 MB/s
dd + pv     310.00 MB/s
cat + pv    347.00 MB/s
ioping        8.58 MB/s
fio         992.78 MB/s

3. New 256GB USB Stick (Slow USB Port)

hdparm       37.60 MB/s
dd           39.86 MB/s
dd + pv      38.13 MB/s
cat + pv     40.30 MB/s
ioping        6.88 MB/s
fio          73.52 MB/s

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Observations

• The old USB stick is not only limited in capacity but also very slow. It barely breaks 20 MB/s in most tests.
• The new USB stick, when plugged into a fast USB 3.0 port, is significantly faster—over 10x the speed in most benchmarks.
• Plugging the same new stick into a slower port dramatically reduces its performance—a good reminder to check where you plug it in.
• Tools like hdparm, dd, and cat + pv give relatively consistent results. However, ioping and fio behave differently due to the way they access data—random access or block size differences can impact results.

Also worth noting: the metal casing of the new USB stick gets warm after a few test runs, unlike the old plastic one.

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Conclusion

Using ChatGPT to develop this benchmark script was like pair-programming with an always-available assistant. It accelerated development, helped troubleshoot weird edge cases, and made the script more polished than if I had done it alone.

If you want to test your own USB drives—or ensure you’re using the best port for speed—this benchmark script is a great tool to have in your kit. And if you’re looking to learn shell scripting, pairing with ChatGPT is an excellent way to level up.

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Want the script?
I’ll share the full version of the script and instructions on how to use it in a follow-up post. Stay tuned!