freebsd stable - Sep 2011 - 7-stable: Root mount problem (mpt, probing / timing related)

Hi,

I've updated a server with mpt controller to the latest
7-stable (ok, it's 7-stable from last week).  During the
boot sequence, the disk connected to the mpt controller (da0)
seems to be probed too late, i.e. just _after_ the kernel
tries to mount the root file system.  It's just a fraction
of a second too late.

This is a screen shot of the situation:

http://www.secnetix.de/olli/tmp2/screenshot-boot.jpg

Of course, I can enter "ufs:da0s1a" at the rootmount prompt,
and the machine continues to boot fine.  But this is a
server that should be able to boot unattended, so I need
this to be fixed.

What's the "official" way to fix this?  I think someone else
had a similar problem some time ago, but a quick search of
the lists doesn't yield anything.

(BTW:  Interestingly, the same machine boots fine without
hickup when booting 8-stable which is installed on another
Slice of the same disk.  This could be just coincidence,
maybe the timing of probing is slightly different between
7-stable and 8-stable.)

Best regards
   Oliver


-- 
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
Handelsregister: Registergericht Muenchen, HRA 74606,  Gesch?ftsfuehrung:
secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht M?n-
chen, HRB 125758,  Gesch?ftsf?hrer: Maik Bachmann, Olaf Erb, Ralf Gebhart

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characters."
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On Tue, Sep 20, 2011 at 03:41:58PM +0200, Oliver Fromme
wrote:
> Hi,
> 
> I've updated a server with mpt controller to the latest
> 7-stable (ok, it's 7-stable from last week).  During the
> boot sequence, the disk connected to the mpt controller (da0)
> seems to be probed too late, i.e. just _after_ the kernel
> tries to mount the root file system.  It's just a fraction
> of a second too late.
> 
> This is a screen shot of the situation:
> 
> http://www.secnetix.de/olli/tmp2/screenshot-boot.jpg
> 
> Of course, I can enter "ufs:da0s1a" at the rootmount prompt,
> and the machine continues to boot fine.  But this is a
> server that should be able to boot unattended, so I need
> this to be fixed.
> 
> What's the "official" way to fix this?  I think someone else
> had a similar problem some time ago, but a quick search of
> the lists doesn't yield anything.
> 
> (BTW:  Interestingly, the same machine boots fine without
> hickup when booting 8-stable which is installed on another
> Slice of the same disk.  This could be just coincidence,
> maybe the timing of probing is slightly different between
> 7-stable and 8-stable.)
Does increasing the 

kern.cam.scsi_delay

loader tunable help at all?

Gary