A / with XFS on RAID5 with an external log

[asjo@koldfront.dk (Adam Sjøgren)]

  Hi.


This is my first post to the mailinglist, so I hope you'll bear with
me. I've spent quite some time spent the last four days searching,
reading, experimenting trying to find the solution to the following
question:


I'm experimenting on a box with three disks with having a root
filesystem on XFS on RAID5. I'm having problems booting Linux if I
have an external log (as recommended in the faq). I've tried with
2.4.18 with the 2.4.18-patch from the ftp-server and with 2.4.14 with
the 1.0.2 patch as distributed by Debian.

My setup is three identical disks that look like this:

 hda1 small /boot
 hda2 raid1 for the log (md1)
 hda3 swap/temporary ext2fs-root while experimenting
 hda4 raid5 for my xfs-/ (md0)

Now, I 'mkfs.xfs -l logdev=/dev/md1 /dev/md0', and the fs is
created. I can mount it with 'mount -o logdev=/dev/md1 /dev/md0 /mnt'
and copy stuff to it. That's all fine.

But when I configure lilo to use /dev/md0 as root and reboot, I can't
make it work. I have different scenarios depending on what I try:

 *) Without initrd and no options: Linux boots and gets to the
    point where it tries to mount / - it then says that xfs needs a
    logdev-option to mount the partition, and the kernel panics.

 *) Without initrd and passing LILO linux rootflags=logdev=/dev/md1:
    Linux boots, EXT2fs complains that it doesn't know what to do with
    logdev, and I get a kernel oops (when XFS tries to mount?)

 *) Without initrd and passing LILO linux rootflags="logdev=/dev/md1"
    (wrong format for option): Linux boots, EXT2fs complains about
    "log, XFS complains about "log - the root fs isn't mounted, and
    the kernel panics.

 *) If I build the kernel with initrd and tell lilo to use it, XFS
    complains about the lacking logdev-option. I've searched and read
    and it seems to me that it should be extremely simple to make an
    initrd that mounts /dev/md0 as / with logdev=/dev/md1, but none of
    the stuff I've found has been "cookbook" enough to give me a clue
    about how.

I'm using Debians kernel-package' make-kpkg (with/without --initrd) to
build a kernel-image-package which I then install.

If someone could point me in the right direction, I'd be very happy.

I don't want to install a lot of stuff on an xfs-filesystem with an
internal log (which I _can_ get Linux to mount when booting, it's not
all misery :-)) when/if I can't (easily) change from internal to
external later on...


  Best regards,

    Adam.

-- 
 "Well, I'm a moon around you"                                 Adam Sjøgren
                                                          asjo@koldfront.dk