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

[Oliver Fromme]

Gary Palmer wrote:
 > 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?

It seems to help ...  I have now rebooted three times with
scsi_delay set to 10000, and it worked so far (the problem
did not always occur before, so I have to try several times).
A value of 5000 was not sufficient.

First I had tried kern.cam.boot_delay, which seems to be
specifically for this kind of situation (according to the
description), but it didn't help at all.  Even very large
values didn't help; I tried up to 30000.

I'm a little surprised that scsi_delay helps, but boot_delay
doesn't.  I would have expected it to be the other way round.

Anyway -- Thank you very much for the hint!

Best regards
   Oliver


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