The Hidden I/O Bottleneck Lurking in Your Linux System
The Hidden I/O Bottleneck Lurking in Your Linux System
Have you ever tuned vm.dirty_ratio? If not, your Linux system might be quietly throttling your disk performance without you noticing. 😬
I took a look at a small RHEL 10 VM and found this:
What does this mean?
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✅ When dirty pages reach 10% of RAM, Linux starts flushing data to disk in the background.
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🚨 At 30%, the kernel blocks new writes until it flushes dirty data to avoid overloading the system.
On this VM with 951MiB RAM, that translates to:
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Background flush kicks in at about 95MiB of dirty data.
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A hard stop happens at around 285MiB.
If you’re running a logging-heavy app or working with slow storage, expect those sudden latency spikes. ⚡
Quick tip to smooth out I/O spikes:
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Set
dirty_ratioto 15 -
Set
dirty_background_ratioto 5
This simple adjustment can prevent unexpected stalls, especially on memory-limited or I/O-sensitive systems.
Remember — better performance isn’t always about more RAM or faster CPUs. Sometimes it’s about mastering how your system manages data flow behind the scenes.
