[NTLUG:Discuss] Mandrake 7 and bootable RAID

[Dan Carlson]

I spent a good deal of time over the weekend installing Mandrake 7 into a
bootable RAID 1 partition.  The good news is that Mandrake 7 does indeed
support installing into a bootable RAID partition.  The bad news is that
there appears to be some problems that can make the process difficult and
frustrating for a while, at least for me.

It makes sense that Mandrake 7 supports installing into a bootable RAID
partition.  RedHat supports this, so since Mandrake is based on RedHat,
unless they were removing functionality, Mandrake should support it too.

If you want to run RAID on large IDE disks (over 33.8 MB) then Mandrake 7 is
a good distribution choice because it uses kernel 2.2.14, which is required
for properly handling large IDE disks, and with some effort and possibly
trial and error, you can install it into a bootable RAID partition.

Overall I thought Mandrake's install program and its disk partitioning and
RAID setup implementation were well thought out and executed.

One install problem that I experienced that was unrelated to RAID was that
whenever the install program would probe the PCI bus for SCSI or display
adapters, it would crash the system hard and power would have to be cycled.
I am running on a fairly generic 440BX-based system board, so I don't know
what would cause this problem.  The workaround was to use the 'Expert'
install mode.  In expert mode they prompt before probing the bus.  Decline
the probe and the install proceeds normally.

The RAID related install problem was that when I would select 'Server'
install, and then manually select all packages on the screen that followed,
the install would proceed normally and it would look like it worked, but
when the system would reboot the kernel would panic.  Inspecting the
messages you could see that the RAID array was not in a valid state and that
this apparently caused the kernel to panic.

Interestingly, if I would NOT manually select all packages for installation,
the install would complete, the system would reboot, the kernel would load
correctly, and everything would work great.

After repeating these and several other install variations, it appeared to
me that if you were installing so many packages that the RAID reconstruction
process started during the install had time to complete before the install
completed, that then this was when the kernel panic problem would occur.  If
I installed a small enough number of packages (that therefore installed
quickly) and the RAID reconstruction did not complete before the installer
rebooted the system, then the kernel panic did not occur.  So it appears
that their installer doesn't properly shutdown the RAID array unless the
reconstruction is still in progress at the time it reboots the system.  This
seems counterintuitive and backward from what I would expect with a problem
like this, but that is how it appeared to me.

You can check the status of the RAID reconstruction during the install by
hitting Ctrl+Alt+F2 to get to a command prompt, then 'cat /proc/mdstat'.
You can effect how long RAID reconstruction takes and therefore whether or
not it is still running at the end of the install by installing fewer
packages, answering install prompts promptly, and using different size RAID
arrays, with larger arrays taking more time to reconstruct.

After playing around with it some more I discovered that I could get the
'Development' install, which is a fairly complete install, to install
quickly enough to work by answering prompts promptly, not installing any
extra packages during install, not downloading any cryptographic packages,
and not creating a boot diskette.  I installed into a 2 GB RAID 1 array on a
Celeron 500 CPU.  After the install completed I went back and used kpackage
to install the extra packages I needed, and I created a second 37+ GB RAID 1
partition to fill out the rest of the Maxtor 40 GB drives I am using.

If any one else tries this or has experience installing into bootable RAID
arrays on large IDE disks, I'd be interested in hearing about your
experiences.

Dan Carlson