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Tech 22 Sep 2026 5 min read

Linux Buffered Writes Separate Write Completion from Storage Persistence

A successful buffered write() does not generally mean that the new file data has already reached non-volatile storage. On Linux, the common buffered I/O path places file data in the page cache, marks the affected cache state dirty, and lets storage I/O occur later. That separation is central to normal filesystem I/O. Memory absorbs application writes at CPU-accessible speed, while the kernel can schedule backing-device traffic independently. The result improves flexibility and can reduce immediate storage stalls, but it also creates a boundary between syscall completion and persistence.

Linux Storage

Linux 16 Sep 2026 6 min read

Linux Readahead Expands Sequential Page-Cache Reads

A buffered file read can cause Linux to fetch more data than the application explicitly requested. The extra I/O is readahead: the kernel populates nearby page-cache folios in anticipation of continued access. This behavior sits between application read size and storage request size. A process may issue modest read() calls while the kernel submits larger reads to keep later accesses from waiting on storage. Readahead is page-cache speculation Buffered file I/O normally passes through the page cache. When requested file data is absent, the kernel must arrange I/O for that miss. The readahead path can extend that operation across additional folios that are not yet present in the cache.

Linux Memory