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From: chris@mimsy.umd.edu (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: Re: Different disks with the same name
Message-ID: <21275@mimsy.umd.edu>
Date: 13 Dec 89 18:51:42 GMT
References: <1989Dec13.052939.17192@binky.uucp>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 24

In article <1989Dec13.052939.17192@binky.uucp> roger@binky.uucp
(Roger Taranto) writes:
>However, how do you add two disks that answer to the same name, but 
>have different geometries?

This is a problem indeed.  The root cause is VMS + DSA.  VMS does not
care very much about layout (it just uses contiguous regions) so it is
really only interested in total disk size.  As a result, vendors can
get away with calling a Wren V an `RA90' or `RA82'.  This is rather
similar to having Honda call their newest miracle a `Dodge Omni'.
Yes, they are both cars, but good grief.

>For example, I just added a SI RA90 ... 1629 cylinders, 15 tracks/cyl,
>69 sectors/track.  At boot time, it tells the kernel that it is a RA90.
>However ... a genuine RA90 ... is: 2649 cylinders, 13 tracks/cyl,
>69 sectors/track.  It too says that it's a RA90.  So, how do you handle
>this since 4.3BSD puts the partition table in the kernel instead of
>on the disk?

Get 4.3BSD-tahoe, which can tell fakes from Gen-Yoo-Wine DECwreck disks,
and which puts the partition tables on the media.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@cs.umd.edu	Path:	uunet!mimsy!chris