Re: Help with CHS / geometry

[Julian Coleman <jdc%coris.org.uk@localhost>]

Hi all,

> > sd0: 8715 MB, 8387 cyl, 10 head, 212 sec, 512 bytes/sect x 17850000 sectors

> The last 17850000 - 17780440 = 69560 sectors will not be accessible with
> this "virtual" geometry and a sun label. The kernel will print a note
> about this on boot, but this is fine (and it happens for a lot of
> "real" drives).

Just a historical note.  Sun used a variety of hardware vendors for disks,
and any Sun label would be compatible with all those vendors.  For example,
the "SUN9.0G" disk would be the same for (e.g.) Seagate and IBM disks, even
though they would have slightly different geometries:

> But the drive has 17850000 sectors, as it does not really have that geometry
> physically (and nothing cares much about that fact).

The big advantage of the common label was when replacing hardware - you could
just put in a compatible drive (i.e. any Sun9.0G drive) without having to
look for the exact vendor and model combination (and that works very nicely
with Raidframe, too!).  However, with NetBSD, you could also use the real
number of sectors, if you wanted the extra space and weren't worried about
compatbility.

Regards,

Julian

--