How does CAM determine the order to number drives ?

Mike Bristow mike at urgle.com
Sun Aug 1 14:27:48 PDT 2004


On Sun, Aug 01, 2004 at 11:36:10AM -0400, Michael Grant wrote:
> I just want to toss this out as an idea: Would it be possible to put
> some identifier somewhere on the drive itself when you partition the
> drive such that the drive itself could always come up in the same
> place regardless even if it moved to a different controller?

Yes.  GEOM in FreeBSD 5.x does this (with geom_vol_ffs).  Basically,
devices with a FFS filesystem with a volume name of "foo" appear
in '/dev/vol/foo'.

I use this for my Soekris box; I don't know if an image I'm building
will appear on /dev/ad0s1 or /dev/ad0s2; so I label the filesystem
with a timestamp and stuff /dev/vol/<timestamp> in /etc/fstab.  That
way I can dd the image onto either slice.  The same principle applies
to disk locations.


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