Many IO benchmark tools (fio, dd, etc...) provide way to set block size.

Lets say that I change 4K to 64k and test read/write on mounted SATA disk. I will get higher data throughput in sequential case of course.

What exactly is influenced by this change, or better, does it really influence underlying file system block size?


For dd, setting the block size simply tells dd how many bytes to read in each read-store-output cycle.

bs=nnn has no impact on filesystem block size, as dd operates on raw devices or binary files, treating input simply as a stream of bytes, and does not know about filesystems.

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