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Date:      Thu, 28 May 1998 19:49:04 -0400
From:      tcobb <tcobb@staff.circle.net>
To:        "'freebsd-current@freebsd.org'" <freebsd-current@FreeBSD.ORG>, "'freebsd-scsi@freebsd.org'" <freebsd-scsi@FreeBSD.ORG>
Cc:        "'simon@simon-shapiro.org'" <simon@simon-shapiro.org>
Subject:   DPT driver fails and panics with Degraded Array
Message-ID:  <509A2986E5C5D111B7DD0060082F32A402FABC@freya.circle.net>

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I have a DPT3344UW/2 running an external 24GB array.  OS is FreeBSD
CURRENT circa 5/18/98.  I'm running the latest available firmware flash
for the card, all on a P5-233MMX with 128MB RAM.

Recently I lost a harddrive in my 24GB RAID5 array.  The array was
configured with a HOT SPARE which should have allowed it to rebuild
completely online, with no interruption in service (except some minor
slowdowns, perhaps).  While the HARDWARE worked well, the DPT DRIVER
failed miserably.

When my array went into degraded mode, the DPT DRIVER froze access to
the partitions.  Upon reboot, during device probe, the DPT DRIVER
returned a 1 SECTOR (0 MB) sense for the array, despite the fact that
the array was operating properly (though degraded).  After this, the
kernel panic'd before completing the boot process with a "Page Fault in
Supervisor Mode" error, and continued to panic this way until the DPT
Array was COMPLETELY REBUILT OFFLINE (requiring me to boot into DOS and
do it - doing the rebuild of that size RAID5 array takes more than an
hour).  After a complete rebuild, the DPT DRIVER showed the array sizes
correctly.

During this process, booting into DOS revealed the array to be fine,
even while the array was degraded -- it also wasn't confused by degraded
mode and showed correct partition information.

I believe that the DPT DRIVER is not correctly sensing that the array is
okay, even though it is in degraded mode, and incorrectly returns
sector/MB values which panic the kernel.  I don't recommend depending on
the proper operation of this driver for your High-Availability needs.

HISTORY
I've used DPT in FreeBSD since last November, first with the hacked
2.2.2 driver.  I upgraded to 2.2.6 to fix a MBUF leak that was crashing
me about once per week.  As 2.2.6, the MBUF leak disappeared and was
replaced with a once every 2-3 day panic which it appeared was not going
to get fixed by anyone (bidone: buffer not busy).  So, I bit the bullet
and upgraded recently to 3.0, which seemed to fix both of these prior
panics only to reveal that the supposedly "high availability" software
driver for my HA hardware is miserable during the most critical times.

-Troy Cobb
 Circle Net, Inc.
 http://www.circle.net

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