new hdd numeration after mainboard change

[Jeremy Chadwick]

On Mon, Oct 13, 2008 at 07:12:20PM +0200, ilikefbsd at web.de wrote:
> i run "FreeBSD  7.1-PRERELEASE" i had a change of the mainboard of my
> lenovo notebook t60. after reboot the harddisk which was before
> recognized as "ad0" is now "ad4". i cannot find any other devices, no
> ad0/ad1/ad2 in /dev. even in the dmesg only ad4

The T60 is a laptop.  It only has one hard disk -- so I'm not sure why
you were seeing ad0, ad1, ad2 in the past.  You shouldn't have been,
unless you had 3 hard disks hooked up somehow.

The bottom line here is this: absolutely *nothing* requires the device
numbering to start at zero.  And this is definitely the case.

> does fbsd create a uniqe identifier for harddisks in combination with
> the motherboard or something like that?  where can i dig further into
> that issue?

It's not really an "issue".  Very likely your computer has toggled some
BIOS settings.

The T60 series has the ability to run the SATA ports in two modes: AHCI,
or Enhanced/Compatible.  Chances are before the motherboard swap, yours
was running in the opposite mode that it is now.

I would highly recommend using the AHCI mode.  It works quite well with
FreeBSD under Intel controllers.  Turn AHCI on (if it's not already),
and do not mess with it.

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |