[arch-general] Can't boot from /usr on LVM

[Michael Schmarck]

Hello.

Last week, I installed Archlinux-i686-2007.08-2.ftp.iso on my system. 
I'd like to have / on /dev/sda3 (PATA) and /usr on /dev/sys/ArchUSR.
"sys" is a LVM2 Volume Group, which I also use in my Gentoo Linux 
installation on the same system.

I've read some installation guides on the Arch Wiki and changed 
USELVM=YES in /etc/rc.conf and have this in mkinitcpio.conf:

HOOKS="base udev keymap autodetect pata lvm2 filesystems"

After changing that line, I re-ran mkinitcpio and a new img was
created; this image is loaded through grub; menu.lst has:

title Arch
kernel (hd0,2)/boot/vmlinuz26 root=/dev/sda3
initrd (hd0,2)/boot/kernel26.img

In /etc/fstab of the Arch installation, I've got:

/dev/sda5		swap		swap		defaults
proc			/proc		proc		defaults
usbfs			/proc/bus/usb	usbfs		defaults
sysfs			/sys		sysfs		defaults
udev			/dev		tmpfs		defaults,size=8m
devpts			/dev/pts	devpts		defaults
devshm			/dev/shm	tmpfs		nodev,nosuid,noexec
temp			/tmp		tmpfs		defaults
/dev/sda3		/		ext3		noatime		0 2
/dev/mapper/sys-ArchArch /Arch		ext3		noatime		0 2
/dev/sys/ArchUSR	/usr		ext3		noatime		0 2

When I boot the system, I see that the "sys" VG gets activated and
fsck.ext3 is run for /dev/sys/ArchArch and /dev/sys/ArchUSR (messages
to the effect that such-and-such fragmentation exists shows and before
that, something like LVM [done]). BUT: I can't boot. Booting stops with:

mount: special device /dev/mapper/sys-ArchArch does not exist
mount: special device /dev/sys/ArchUSR does not exist

This shows, that both "paths" are not accessible; neither the /dev/sys/*
stuff (which on a Gentoo Linux installation contains symlinks to /dev/mapper),
nor the "proper" /dev/mapper path can be accessed.

Any ideas about why that happens, and, more importantly, how to fix
that?

Thanks a lot,
Michael