If you’ve ever worked on performance issues with an IO- intensive app, there is a good chance you already know that the application performance degrades when the disks are stressed out. This fact is usually well known, but the reasons behind it aren’t always clear. I’d like to try and clarify what’s going on behind the scenes.

In a typical scenario, when data is written to a file, it is first written to a memory area reserved as the page cache.

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