How does CAM determine the order to number drives ?

[Dmitry Morozovsky]

On Sat, 31 Jul 2004, Michael Grant wrote:

MG> Yes, I know this situation all to well.  In my case, I ended up
MG> physically plugging and unplugging drives until they ended up in the
MG> right place.
MG>
MG> I would sure love to see a way to fix a drive to an identifier.  This
MG> has to be the one thing that has wasted more of my time than anything
MG> else in freebsd.  For example, when I had a drive die on me a couple
MG> months back, when the machine rebooted, the dead drive still in the
MG> system, da2 became da1 and things just did not work well.
MG>
MG> If someone knows of a way to tie physical drives to the nodes in /dev,
MG> please let me know.  I've heard that this auto drive numbering
MG> is a bios "feature" which is impossible to get around.

root_disk_unit="2"

in /boot/loader.conf ?

MG>
MG> Michael Grant
MG>
MG> On Sat, Jul 31, 2004 at 08:25:58PM +0100, Pete French wrote:
MG> > Hi, I have a small server which boots from an
MG> > Adaptec 2940 controller under CAM, and serves drives
MG> > off a Compaq 4200 RAID controller.
MG> >
MG> > I have spent the afternoon ttrying to upgrade the
MG> > RAID controller from a 4200 to a 5300. The 5300 uses
MG> > the CISS driver rather than the IDA driver, and this
MG> > lives under CAM too. Thus my RAID drives have changed
MG> > from being idad devices to being da devices.
MG> >
MG> > Unfortunately the RAID controller gets scanned first
MG> > so I now have a da0 and a da1 where I didnt before, and my
MG> > root drive has moved to da2.
MG> >
MG> > I can't persuade it to boot like this - it refuses to mount
MG> > the root from da2. The simplest solution, of course, would
MG> > be to somehow force the CAM system to scan the Adaptec
MG> > controller first, so that the root device is back in da0
MG> > where it belongs. But I cant find out if there is a way
MG> > of dojing this, or indeed how the system determines the order
MG> > at all.
MG> >
MG> > Any suggestions ?
MG> >
MG> > -pcf.
MG> >
MG> > PS: System is 4.10-RELEASE, though I suspect this is irrelevent
MG> > _______________________________________________
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MG>

Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck at rinet.ru ***
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