It’s really the hardware block size that matters in this case (direct I/O). That value is a property of the hardware and can’t be changed.
In some situations, the “logical” block size can differ. For example, buffered writes use the page cache, which operates in PAGE_SIZE blocks (usually 4K). Or your RAID stripe size might be misconfigured, stuff like that. Otherwise they should be equal for best outcomes.
In general, we want it to be as small as possible!
In some situations, the “logical” block size can differ. For example, buffered writes use the page cache, which operates in PAGE_SIZE blocks (usually 4K). Or your RAID stripe size might be misconfigured, stuff like that. Otherwise they should be equal for best outcomes.
In general, we want it to be as small as possible!