weird partitioning problem

[akelder]

Hello,

I have a problem I can't figure out for the life of me: fdisk, the
GUI partitioning tool, df and mount see a drive and partitions that are not there
anymore.

Here's what happened:

Based on good reviews, I purchased the Areca ARC-1110 RAID 4-port
SATA PCI-X controller. I had a hard time installing openSUSE because
the installer couldn't see the array. I've tried a bunch of things
like compiling a driver from source or using the vendor provided driver
and feeding it to the installer, but nothing worked.

Finally, I plugged in a standalone 80gb SATA drive, installed
openSUSE 10.2 on it, downloaded the 2.6.19.1 kernel from kernel.org,
compiled it using the standard SUSE kernel config file (only difference
was enabling the arcmsr driver, which starting with the 2.6.19.x kernel
is in the mainline), then installed the newly built kernel rpm package
on my system.

Succe-ess! (in Borat voice). The OS now could see the RAID
volume. Setup three partitions on the RAID volume (swap, root, home)
and copied the root directory from the SATA drive to the RAID volume,
e.g. from /dev/sda2 to /dev/sdb2. After that I was able to boot into
the OS on the 80GB drive by choosing HD0,1 and sda2 in GRUB or on the
RAID vol (HD1,1 and sdb2). Success again. Then disabled the
standalone SATA drive in the BIOS, so, from the GRUB bootloader
perspective, what used to be my second drive (RAID array) became my
first, e.g. HD1,1 sdb2, became HD0,1 and sda2.

However, once booted, my system still "sees" the old drive and
partitions:

bfs1:~ # fdisk -l

Disk /dev/sda: 80.0 GB, 80000000000 bytes
255 heads, 63 sectors/track, 9726 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 1 262 2104483+ 82 Linux swap /
Solaris
/dev/sda2 * 263 2873 20972857+ 83 Linux

Disk /dev/sdb: 1499.9 GB, 1499999502336 bytes
255 heads, 63 sectors/track, 182364 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 262 2104483+ 82 Linux swap /
Solaris
/dev/sdb2 * 263 6790 52436160 83 Linux
/dev/sdb3 6791 182364 1410298155 83 Linux

And df and mount show that my filesystems are mounted on sdb, as if the
standalone SATA drive was still present:

bfs1:~ # df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sdb2 20641788 3248328 16344820 17% /
/dev/sdb3 1388169056 209056 1317445096 1% /home

bfs1:~ # mount
/dev/sdb2 on / type ext3 (rw,acl,user_xattr)
/dev/sdb3 on /home type ext3 (rw)

Everything works, but I'm just confused as to why this is happening.
Help!!! thanks in advance, -Alain.

[akelder]

Mr John-Paul Stewart cleared up my confusion with the following answer on another forum:

This is expected behaviour. The Linux kernel doesn't use the BIOS for
disk access (the BIOS is only used by GRUB/LILO before the kernel is
loaded). So since the kernel isn't using the BIOS, how would the kernel
know that the disk is disabled in the BIOS? It won't, so it will use
the drive.

(This is actually a handy feature on older systems where the BIOS will
complain about very large modern drives. Disable the drive in the BIOS
to make it happy, but retain full access to the drive after booting.)

If you don't want the kernel to see the drive, you have to physically
remove it or prevent the kernel from loading the driver for its
controller (which may or may not be possible, depending on a number of
factors).

I unplugged the 80GB drive and he's right: Linux no longer sees it. Brilliant.

Interestingly, for my "sanity check", I had booted the box to a WinPE
(BartPE) CD and viewed the storage environment with various tools, none
saw the disk that was disabled in the BIOS. Guess WinPE somehow
"honors" the BIOS setting?

[rong]

That's good info. Thanks for following up with the solution.