It's not quite as simple as that when you're dealing with pipelines. For example: cat /dev/zero | strace dd bs=1M of=/dev/null will show that you're not a

It's not quite as simple as that when you're dealing with pipelines. For example: cat /dev/zero | strace dd bs=1M of=/dev/null will show that you're not actually writing 1M blocks. You're just reading whatever `cat` outputs (128KiB blocks on my system), so all you've done is an unnecessary pipe and copy. You would have been better off just redirecting. Similarly, dd if=/dev/zero bs=1M | strace gzip -1 > /dev/null will show you that `gzip` will not start processing larger blocks. You're just adding an additional copy. Linux already has readahead, so I don't know if you'll ever see a benefit to this. On my system, adding dd with higher block size on both sides of a gzip -1 pipeline just ends up being slower.