how to make fixed Direct Access device (da) ID

[Robert Marella]

On Sat, 16 Sep 2006 13:05:11 -0700
"Jin Guojun [VFFS]" <jin at george.lbl.gov> wrote:

> It is awkward that dynamically and/or statically attaching SCSI hard 
> drive and
> USB hard drive to the system will have different da IDs.
> For example, boot system with a SCSI drive (SCSI = 1), will have a
> da0 for this
> SCSI drive. Then plugging in a USB hard drive, which will be
> configured as da1.
> 
> If boot system with both drives online, system will boot from SCSI
> drive fine till
> mounting root point. It fails because USB drive has da0 and SCSI
> drive has da1.
> 
> Is there anyway to configure the system to have fixed da ID for SCSI 
> drive or
> even for USB drive regardless if they are dynamically/statically 
> attached to the
> system?
> 
>     -Jin

Hello Jin

Try man (4) scsi:

 All devices and the SCSI busses support boot time allocation so that an
     upper number of devices and controllers does not need to be
configured; device da0 will suffice for any number of disk drivers.

     The devices are either wired so they appear as a particular device
unit or counted so that they appear as the next available unused unit.

     Units are wired down by setting kernel environment hints.  This is
usu- ally done either interactively from the loader(8), or
automatically via the /boot/device.hints file.  The basic syntax is:

           hint.device.unit.property="value"

     Individual SCSI bus numbers can be wired down to specific
controllers with a config line similar to the following:

           hint.scbus.0.at="ahd1"

     This assigns SCSI bus number 0 to the ahd1 driver instance.  For
con- trollers supporting more than one bus, a particular bus can be
assigned as follows:

           hint.scbus.0.at="ahc1"
           hint.scbus.0.bus="1"

     This assigns SCSI bus 0 to the bus 1 instance on ahc0.  Peripheral
driv- ers can be wired to a specific bus, target, and lun as so:

           hint.da.0.at="scbus0"
           hint.da.0.target="0"
           hint.da.0.unit="0"

     This assigns da0 to target 0, unit (lun) 0 of scbus 0.  Omitting
the tar- get or unit hints will instruct CAM to treat them as wildcards
and use the first respective counted instances.  These examples can be
combined together to allow a peripheral device to be wired to any
particular con- troller, bus, target, and/or unit instance.

     When you have a mixture of wired down and counted devices then the
count- ing begins with the first non-wired down unit for a particular
type. That is, if you have a disk wired down as device da1, then the
first non- wired disk shall come on line as da2.


HTH
Robert