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

[Gary Palmer]

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