AHCI support in 6.1-RELEASE?

Antony Mawer fbsd-questions at mawer.org
Mon Oct 9 18:11:07 PDT 2006

On 10/10/2006 11:02 AM, Juha Saarinen wrote:
> On 10/10/06, Antony Mawer <fbsd-questions at mawer.org> wrote:
>> Most likely this renumbers the drivers, so you go from your hard drive
>> showing as eg. ad0 to ad4. You will need to edit /etc/fstab as
>> appropriate to match what the drive is showing up as after changing to
>> AHCI mode.
> Yep... exactly like that - from ad0 to ad4. Worked perfectly. Thank
> you very much, it didn't occur to me that there would be driver
> renumbering when switching to AHCI.
> Oddly enough, even though the drive is connected to SATA port 0 on the
> motherboard, it shows up as being on ATA channel 2, Master.  According
> to atacontrol, I have six ATA channels on the box, 0-5. Doesn't seem
> quite logical that the driver should be renumbered as ad4, but... if
> it works, I don't care.

Usually I find that ad0/ad1 = primary IDE (master/slave), ad2/3 = 
secondary IDE (master/slave), and then the SATA connectors pick up from 
ad4 onwards...

The SATA ports seem to be numbered in increments of 2, presumably 
because every SATA port is a "master", so the usual "slave" position is 
unused... ie:

     SATA 0 -> ad4
     SATA 1 -> ad6
     SATA 2 -> ad8
     SATA 3 -> ad10

Presumably turning off ATA_STATIC_ID would just number them in the 
sequential order (ad0, ad1, ad2, ...) based on the devices that are 
actually connected... but this can mess things up when you connect 
additional drives at a later date somewhere in the middle of the chain!

I have a patch I wrote for sysinstall somewhere that allows you to do 
disk=auto in an install.cfg, and it picks the first device it comes 
across (eg. if ad4 is the first IDE disk, it picks it over ad10)... 
we've found this very handy for installation/deployment scenarios that 
are automated via install.cfg but may have different disk configurations...

If there's enough interest I might look at submitting it for inclusion...


More information about the freebsd-questions mailing list