Subject: Re: cdev vs. bdev (32 bit dev_t)
To: None <tech-kern@NetBSD.ORG>
From: Giles Lean <>
List: tech-kern
Date: 01/14/1998 07:50:05
On Tue, 13 Jan 1998 09:50:44 -0800  Paul A Vixie wrote:

> One thing about these dev_t's that we havn't discussed is how many subparts
> we need.  HP-UX did three part dev_t's years ago, and I see that BSD/OS 3.*
> has done the same (see below).

I have no opinion about the utility of three part dev_t's, but HP's
implementation in practice caused some problems.

On HP-UX the logical unit numbers (later instance numbers?) were
generated at OS install time via autoconfiguration.

Problem was (is) that the numbers wouldn't generate identically if you
added or removed hardware, and you had to regenerate them if replacing
a root disk*.  This leads to some confusion from time to time, as both
HP customers and Response Centre engineers will tell you!

cgd has been concerned about the maintenance overhead.  I'd like to
raise administrator overhead for consideration, too.


*Yeah, you _can_ manually allocate them.  I used to know the details. :)