Block size for "dd" with floppies

[John H. Robinson, IV]

On Mon, Jul 31, 2000 at 09:11:30PM -0700, Carl Kuck wrote:
> Carl Lowenstein wrote:
> 
> >And, as I just discovered, 
> >	$ time dd if=/dev/fd0 of=/dev/null bs=18k
> >
> >will finish in 0.0 time when you run it again, because the information
> >has been cached in system buffers.
> >
> >My current belief is that Linux buffers the transfer in such a
> >fashion that the block size doesn't make any difference.
> 
> I wonder if the Linux floppy driver is smart enough to know the
> difference if you remove one floppy and insert another...

it is.

[jaqque at osiris:~]% time dd if=/dev/fd0 of=/dev/null bs=512 count=2880
2880+0 records in
2880+0 records out
dd if=/dev/fd0 of=/dev/null bs=512 count=2880  0.01s user 0.10s system 0% cpu 48.500 total
[jaqque at osiris:~]% time dd if=/dev/fd0 of=/dev/null bs=512 count=2880
2880+0 records in
2880+0 records out
dd if=/dev/fd0 of=/dev/null bs=512 count=2880  0.02s user 0.00s system 48% cpu 0.042 total
[jaqque at osiris:~]% time dd if=/dev/fd0 of=/dev/null bs=512 count=2880
2880+0 records in
2880+0 records out
dd if=/dev/fd0 of=/dev/null bs=512 count=2880  0.01s user 0.10s system 0% cpu 48.419 total

right before the third run, i popped out the floppy and popped it bacl
in.

-john