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Date:      Tue, 4 Sep 2007 20:12:25 -0600
From:      Modulok <modulok@gmail.com>
To:        freebsd-geom@freebsd.org
Subject:   Root partition on gmirror, provider not being created at boot time...
Message-ID:  <64c038660709041912w3b7824dal1c6b54704a2821a1@mail.gmail.com>

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A. BACKGROUND -- For the impatient, skip to the last paragraph in section B.
I'm experimenting with gmirror on the root partition on a test system
running FreeBSD 6.1-RELEASE. I have two physical disks on the same IDE
header (primary master and primary slave). The disks are jumpered
correctly, the cables are good, the headers are functioning - both
disks are accessible, operational and detected by FreeBSD.

A gmirror was setup using /dev/ad0 as the first consumer. (The debug
kernel state, kern.geom.debugflags=16 was set to permit using an
already mounted device as a consumer.) The mirror was successfully
created, I then inserted an additional consumer /dev/ad1. The array
auto-synchronized. I edited /etc/fstab and /boot/loader.conf to
automatically load the geom_mirror.ko modules and mount the file
systems from their respective geom providers. After rebooting the
system everything still works and root is mounted from its geom
provider, /dev/mirror/gm0s1a,  correctly. Everything works. Now let's
try to break it....

B. PROBLEMS
I simulated a disk failure on the primary slave disk, by physically
disconnecting the power input and booting the system. This is where I
run into problems:

 1. The BIOS complains of a disk error, but otherwise continues to boot.
 2. The master boot record is found on the primary master and the the
boot manger is executed.
 3. loader(8) is found and presents its menu, it starts the automatic
boot sequence with the GENERIC kernel.
 5. After the kernel probes for various devices, "Trying to mount root
from ufs:/dev/mirror/gm0s1a", fails and I am prompted for the location
of a root partition.

 I digress just a moment here, as the system appears to hang because
keyboard input is not detected and at this point on the boot phase, I
have no other metric from which to judge whether it is actually hanged
or not. The keyboard was detected prior to this failure as reported by
the device probe. So that's weird, but it even if I could type in
something, (?, for example), it wouldn't matter because it's looking
in the correct location for root, it's just that the location doesn't
exist yet.

 The provider, /dev/mirror/gm0, is not being created. This is
significant for obvious reasons: no mirror means no provider which
means no root. The module /boot/kernel/geom_mirror.ko is loaded, as I
have manually loaded it via the loader(8) prompt on several
consecutive attempts to resolve the problem with identical results. As
far as I can tell, it's the provider that isn't being created, for
whatever reason.

C. FAILED RESOLUTIONS -- In each of the possible resolutions below,
the results are the same.
 1. Try to boot with the disk entirely disconnected, data cable included.
 2. Re-install FreeBSD following the method outlined in the handbook.
 3. Manually load the kld via the loader(8) prompt before starting the kernel.
 4. Ensure that the BIOS is not attempting to override with some
onboard hardware mirroring features.
 5. Physically swap disk order, making what was once the primary
slave, the primary master.

D. TO DO -- The following have not yet been attempted:
 1. Email the geom mailing list (...this is where I'm at now...)
 2. Statically compile gmirror into the kernel.
 3. Attempt the same setup and failure scenario on differing hardware.
 4. Attempt the same setup and failure scenario using a different
version of FreeBSD.

E. SYSTEM SPECIFICATIONS -- If it matters.
 Mainboard: Tyan Thunder k7X model S2468 dual socket
 BIOS: Phoenix Bios 4.0 Release 6.0
 Disks: 2x Western Digital EIDE model WD1600SB-01RFA0

Is there anything blatantly obvious that I'm missing or should check
for? I posted a previous version of this thread to freebsd-questions a
few days ago with limited success. Sorry for such a long post.
-Modulok-



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