Subject: Re: strange disks...
To: Tim Shoppa <shoppa@alph01.triumf.ca>
From: Anders Magnusson <ragge@ludd.luth.se>
List: port-vax
Date: 12/30/1997 16:42:01
>
> Then how come "disklabel" still insists on knowing device geometry,
> to the continuing distress of everyone using block-addressable disks?
> Some of the *worst* advice I've seen on the port-vax mailing list
> makes it seem that many still believe this information is important :-(
> I think it ought to be completely banished from the disklabel process
> for MSCP disks, as the geometry is so hidden behind the interface
> that it's difficult to use this information for performance purposes
> (i.e. seek ordering.) Besides, MSCP controllers do their own seek
> ordering, so the OS shouldn't have to screw around with this!
>
The actual geometry of a MSCP disk is gotten from the controller, but
it is not used inside the kernel. If a new unlabeled MSCP disk is attached
to a NetBSD/vax system, a default disklabel is filled in with the
geometry reported from the hardware. The only reason that the disklabel
must be filled in completely when doing a fresh installation is that
the installation tools don't know which disk type it is; it may be
a hp or rd or whatever disk that must have their geometry in the disklabel.
The MSCP disk device driver doesn't use any seek ordering at all.
Other drivers like the hp driver does.
The installation tools will change to a much easier system in the
near future.
-- Ragge