adding disk moves ad0 to ad4

Steve Franks bahamasfranks at
Wed Feb 3 18:21:56 UTC 2010

On Wed, Feb 3, 2010 at 10:54 AM, Polytropon <freebsd at> wrote:
> On Wed, 3 Feb 2010 10:35:48 -0700, Steve Franks <bahamasfranks at> wrote:
>> Just curious, having read the handbook section talking about freebsd
>> going straight to the hardware and skipping the bios for disk
>> numbering, why then, if I stick a sata disk in 'sata0' on the
>> motherboard, does it come up as ad0, but if I add a second disk in
>> 'sata1' or 'pata0', on the next boot, I have no ad0, but ad4 and ad6?
>> This seems to be the case with every mobo I've owned in the last 2
>> years from a variety of mfr's.  Is there a way around this?
> Maybe this is specific to your motherboard. As far as I
> experienced, using (P)ATA and SATA - or not using it -
> keeps the numbering intact, e. g. ad0 - ad3 is ATA,
> ad4 - ad7 is SATA, no matter where a disk is actually
> connected.
> It's possible that your BIOS does something strange in
> representing one SATA, but no ATA disk as ad0, "the first
> disk existing", as well as if an ATA disk would be present,
> but no SATA disk.
> I can understand that this is annoying.
>> I don't
>> care what it comes out as, as long as it stays put...
> There are labels or UFSIDs you can use to identify partitions
> on a disk regardless of the device name they would come
> out as. See "man glabel" and "man tunefs" for details.
>> Since I have
>> the only fbsd system at work, I tend to format alot of funky drives
>> for people, and it gets anoying having to swap fstab's every time...
> Labels can really help here: /etc/fstab will then contain
> labels or UFSIDs instead of device names - and they don't
> change when a disk is added or removed.
> --
> Polytropon
> Magdeburg, Germany
> Happy FreeBSD user since 4.0
> Andra moi ennepe, Mousa, ...

I knew there had to be a solution!  Thanks!


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