> >> As far as reading the source, 3687+7io is 3687 read and 7 write.
> >
> >So, there's one thing which mkdir() does in ffs which is different
> >from other sorts of file creation... it tries to put the directory in
> >a different cylinder group from the one it's parent lives in..
> 
> Hmmm.  Dumb question:  is this intended as a speed optimization or as a
> reliability optimization (I can think of explanations for either :-)).

It's a speed optimization.

> If speed, is this still meaningful with modern disks?

The theory is so that you can go from directory inode to directory
page to file inode to file page with only "small" (faster) seeks most
of the time, and if you have a directory with a bunch of small files,
the file inodes and contents will be near each other.

This sort of thing will be at least slightly relevant as long as disk
heads have inertia.. it's the rotational positioning optimizations
which are questionable these days.

					- Bill