"Steven M. Bellovin" <smb@research.att.com> writes:

> Has anyone revalidated those numbers for modern disks?  When FFS first 
> came out, there was a lot of talk about rotational optimizations, 
> staying within the cylinder, etc.  Nowadays, of course, that's all 
> mythical.  

I believe rotational optimization is mythical due to whole-track
buffering (as well as not knowing the layout), but staying 'close' in
cylinder space probably still helps, in terms of small seeks vs
whole-disk seeks.

It should be possible to figure out the real geometry with timing
experiments, but it seems no one has written a spiffy program to do
this.  It would require considerable thought to avoid getting fooled
by the disk's cache; perhaps it could be done with writes with WC
disabled.

-- 
        Greg Troxel <gdt@ir.bbn.com>